Looking back on the decisions you've made, whether concerning your relationships, education, career, or even how you've spent your money, would you love an opportunity to go back in time and change a few things? If you are one of the very few people who would boldly claim they would make the same decisions over and over again, you are special. Most people would change many things about themselves, but most importantly, they'd take advantage of the opportunities they let slip through their fingers.

Regardless of the great strides we have made in any field, chances are we will never find a way of seeing into the future. If any individual could see as far into the future as they would want, they would rule the world.

Here is a list of celebrities who turned down movie roles for different reasons. In most of these cases, the actors who eventually took on the roles became very successful afterwards, and some have even been awarded the most coveted awards out there. If the actors who were supposed to play these famous roles knew what they know now, chances are they would have never let these roles go. The good news is that these famous actors are only human, and thanks to the choices they made, we have even more talent in Hollywood.

Sam Claflin As Jon Snow (Game Of Thrones) 

Would you imagine anyone playing the role of Jon Snow in the hit series Game of Thrones other than Kit Harington? I bet your answer is a big "NO." This is because we have grown to love how he plays this role, and we are convinced no one else could do a better job. When Alliser Thorne and men of the Night's Watch killed Jon in the last episode of season 5, fans from all over the world expressed their sadness and the show had to find a way of resurrecting him.

Now, imagine how the show would have been if Sam Claflin played the role of Jon Snow. Would we love him as much as we love Kit? We might have, but most of us don't want to think about it too much because we are loyal to the Jon Snow we know and love. This Hunger Games star had auditioned for this role and that of Viserys Targaryen, two very different roles, but it makes sense because of the relationship these two have with the Khaleesi.

Tom Cruise As Iron Man (Iron Man)

Iron Man is one of Marvel's most loved superheroes, and some fans will even claim he is the most powerful. The best things about Iron Man are his numerous suits and J.A.R.V.I.S, which work together to make him the most powerful and likeable superhero in the Marvel Universe. Tony Stark's personality has a lot to do with the love he receives across the globe, and it's hard to think of Stark played by anyone else other than Robert Downey Jr.

However, did you know Tom Cruise was originally supposed to play this role? Cruise can do many things except disappoint his audiences, which is the reason it would have been so exciting to see him play this or any other superhero role. Cruise can be smart, sarcastic, and fight better than most actors can, which are qualities that prove he would have been a great Iron Man. However, when the script was ready, Cruise thought it wasn't as strong as he had imagined, so he turned it down and Robert Downey Jr. stepped up.

Britney Spears As Allie (The Notebook)

Britney Spears has many talents, which include singing, dancing, and acting. However, we can all agree her greatest strength lies in singing. Britney is one of the most successful musicians of all time; she has sold over 150 million records around the world, sold 22.38 million singles through digital downloads, and won numerous prestigious awards.

Britney is on this list because she almost played the role of Allie in one of the most well-known romantic movies of all time, The Notebook. We aren't quite sure she would have played the character as well as Rachel McAdams, but apparently, she was great during the auditions.

Although at one point during the shooting of the film, Ryan Gosling and Rachel McAdams couldn't stand each other, they went on to win an MTV award and date for at least three and a half years. Things would probably have turned out differently if Britney got the part, since she would have been reuniting with Gosling, who she acted alongside in The All New Mickey Mouse Club.

David Schwimmer As Agent J (Men In Black)

The Men in Black films are some of the best science fiction spy films out there, and they are based on the Marvel comic book series called The Men in Black. The highly-funded secret organization has agents everywhere on earth whose mission is to protect the earth and its citizens against aliens and the knowledge of alien activities on earth.

We have become so familiar with Tommy Lee Jones and Will Smith playing the roles of agents Kay and Jay respectively, it was a surprise how easily we embraced Josh Brolin as the younger version of agent Kay. Therefore, it will surprise many to hear that David Schwimmer turned down the role of Agent J, which Will Smith took up and it became one of his best career moves. It's now hard to think of MIB without thinking about Will Smith, owing to how great he is in all the three films so far.

Julia Roberts As Catherine Tramell (Basic Instinct) 

Throughout the 1990s and half of the 2000s, the title of the highest-paid actress in the world belonged to Julia Roberts because she was, and continues to be, such a great actress. Her success over the years has made her a darling to many, and her beauty has led People's magazine to name her the World's Most Beautiful Woman five times.

With such success, it's obvious why producers approached her to play the role of Catherine Tramell in Basic Instinct, which she declined owing to the amount of violence, nudity, and explicit love scenes involved. Other women, including Kim Basinger, Meg Ryan, Greta Scacchi, and Michelle Pfeiffer turned it down for similar reasons as well.

Sharon Stone, who at the time was relatively unknown, took up the part and made the film amazing. The film was a huge success all-round, in addition to allowing her to win a Golden Globe Award and making her a s*x symbol.

Will Smith As Neo (The Matrix)

Will Smith is one of the greatest actors of all time, and you just need to watch one of his movies to believe this. One quality all great actors have is the ability to choose to participate in a film or a series with the potential of becoming a hit, because the bigger it gets, the more the actor makes and becomes famous.

However, when Will Smith turned down the offer to play Neo in The Matrix, we can all say he made a terrible decision, which cost him the opportunity to change Hollywood and become an even greater actor. The Matrix films are still revolutionary and unique in terms of their action and effects and it will be a while before another film or franchise will catch up with them.

Will Smith claimed he turned down the offer, and he felt as if he would have messed it up after seeing Keanu Reeves' performance, which we can all agree was outstanding.

Kate Winslet As Viola (Shakespeare In Love)

When we think about Kate Winslet, we always remember her outstanding performance in Titanic, the epic 1997 film, which propelled her and Leonardo DiCaprio to stardom. This film about the ill-fated maiden voyage of the then-massive Titanic was a huge box office success, and it continues to make people cry even today.

Kate Winslet's performance as Rose DeWitt Bukater in the film was so good it earned her an Academy Award nomination for Best Actress. Surprisingly, James Cameron wanted to cast Gwyneth Paltrow for the part, but Winslet campaigned for the role and got it, becoming one of her best performances on screen.

Weirdly, Winslet was offered to play Viola in Shakespeare in Love, but she declined, citing a desire to put more effort on her independent films. Gwyneth got the part, and she ended up winning an Oscar for her performance. It's funny how a great opportunity can come knocking on your door and you turn it down, paving the way for someone else's success.

O.J. Simpson As The Terminator (The Terminator) 

Although Arnold Schwarzenegger has been in numerous movies and played so many characters, none of those characters truly stuck with him like the Terminator. Even when he served as the 38th Governor of California for two terms from 2003 to 2011, people called him "The Governator."

Therefore, it's so shocking to learn that O.J. Simpson was supposed to be the Terminator instead of Schwarzenegger. What made him the perfect fit for the role was his level of fitness since he had just retired from playing football. Schwarzenegger was to play the role of the brave soldier, which Michael Biehn eventually played.

Weird enough, one of the main reasons O.J. never got the part was because he was such a pleasant guy and everybody loved him, so he wouldn't have fit the profile perfectly. Besides, back then it wouldn't have been such a great idea to have a film about an African-American man attempting to stab a white girl.

Sandra Bullock As Maggie (Million Dollar Baby)

Sandra Bullock has been acting since 1987 and over the years has achieved great success. Some of her best performances are in films such as Miss Congeniality, Two Weeks Notice, Crash, The Proposal, and The Heat. However, the role that earned her an Academy Award was Leigh Anne Tuohy in the film The Blind Side.

Her performance in the 2013 film Gravity earned her Academy Awards, Golden Globe Awards, and British Academy Film Awards nominations, and she won a Saturn Award for Best Actress. In Minions, Bullock voiced Scarlet Overkill, a super-villain character in an animated film, which became her highest-grossing film.

Bullock is here because she was meant to play the role of Maggie in Million Dollar Baby, which she tried to do, but failed and started concentrating on Miss Congeniality 2. Hilary Swank ended up playing Maggie, and for her performance, she won an Academy Award.

Russell Crowe As Wolverine (X-Men)

It's impossible to think of anyone other than Hugh Jackman playing the role of the Wolverine because he does such a great job bringing the character to life. He plays the character so well that we always expect him to transform into the mutant even when he's not in an X-Men or Logan film.

However, did you know that Russell Crowe, Jackman's friend and fellow Aussie, was the actor who was originally meant to play Wolverine? He turned down the role because he thought a wolverine was a wolf, and he didn't want people to assume he could only play wolf parts. Crowe ended up recommending Jackman for the part, who at the time wasn't well-known, which he accepted, and he became the star we know today. Jackman played this role for 17 years, concluding his contract with the death of the character in Logan.

Nicolas Cage As The Green Goblin (Spider-Man)

Nicolas Cage is undoubtedly one of the most talented actors in Hollywood since he has received a Screen Actors Guild Award, a Golden Globe award, and an Academy Award, including other awards and nominations.

Cage has always been a fan of Marvel and other comic books and has always wanted an opportunity to play a major superhero in a film. He got his chance when he played Johnny Blaze in the Ghost Rider films, as well as Damon Macready in Kick-Ass, but some roles such as playing Iron Man and Superman never materialized.

More recently, Cage got the opportunity to play The Green Goblin in Spider-Man, but he turned it down. Many thought he would have jumped at the opportunity, but he paved way for Willem Dafoe to become the villain we all loved to hate. Probably Cage wanted to play Spider-Man and didn't want to be the bad guy.

Ashton Kutcher As Superman (Superman Returns)

Superman is one of the biggest characters not just in the DC universe but in all of film, so the casting directors can't afford to make a mistake in whom they choose to be the Man of Steel. The people who have played this role have never disappointed us, and Henry Cavill is arguably the best Superman we have had so far.

It's hard to imagine what kind of a Superman Ashton Kutcher would have made since we haven't seen him in a superhero role before. We're used to seeing more of him in comedies, such as Two and a Half Men and The Ranch.

However, Kutcher had auditioned for the role and even did a screen test with the suit on, but he didn’t feel right. In his opinion, he would have needed to work out a bit more before playing such a role, because wearing the fake muscles looked and felt weird.

Jennifer Lawrence As Bella (Twilight) 

Can you imagine how great it would've been if Jennifer Lawrence would've landed the role of Bella in Twilight? So much would have been different now, but it's impossible to tell whether the difference would be good or bad. We can assume that, since Kristen Stewart ended up getting the part, she became everyone's sweetheart, especially when she was "secretly" dating Robert Pattinson. She became a star thanks to the success of the films.

If Jennifer Lawrence had gotten the part, she might have been the one to fall in love with Pattinson. In addition, it's likely she wouldn't have cheated on him with Rupert Sanders and would not have brought so much heartache to all Twilight fans across the globe. However, though she desperately wanted to play the part, she went on to make a name for herself and appeared in films including X-Men and The Hunger Games, and she got involved with Nicholas Hoult.

 Emma Watson As Mia (La La Land)

If you haven't watched La La Land, you seriously need to watch it, because it was arguably the best film of 2016. Critics and audiences everywhere loved this film, since despite working with a production budget of $30 million, it made well over $445 million worldwide.

The film received seven Golden Globe Awards, five British Academy Film Awards, and an outstanding six Academy Awards. Among the prestigious awards, Emma Stone received the Academy Award for Best Actress, which she deserved thanks to her outstanding performance in the film.

Although Stone played the role of Mia so well, Emma Watson was originally supposed to play the role, but she had to turn it down because of scheduling conflicts with Beauty and the Beast. Watson explained she needed to be all in if she would have pulled off her role effectively, yet she had already committed elsewhere. We can only wonder whether she ever questions the decision she made in letting La La Land go.

Taraji P. Henson As Olivia Pope (Scandal)

Did you know the Empire star Taraji P. Henson auditioned for the role of Scandal's Olivia Pope? How crazy is that? Even before she got the opportunity to audition for the role of Cookie Lyon, Taraji read Olivia's part for Shonda Rhimes but confessed that she thought the role suited Kerry Washington while she was there. Weirdly enough, Gabrielle Union also auditioned for the part but didn't get it, although now we understand how difficult it would have been to do this and Being Mary Jane.

Kerry Washington landed this role and we love the fact that she's the Olivia Pope we have known and loved all these years, and we believe no one could have done a better job. Scandal has won numerous awards over the years, with Washington winning the Image Award for Outstanding Actress in a Drama Series for the show and receiving Emmy Award, Golden Globe Award, and SAG Award nominations as well.

Sources: screencrush.com, nme.com, mtv.com, slashfilm.com, cosmopolitan.com, ew.com, moviepilot.com, dailymail.co.uk, independent.co.uk eonline.com, cinemablend.com.