Remakes have been around almost as long as film, but only recently has their been an outcry against them.
Some films do benefit from a remake. Certain science-fiction or fantasy films that required special effects that weren't available at the time can get new life breathed into them. A great example of this is the Lord of the Rings trilogy. While Ralph Bakshi's animated features are classics in their own right, Peter Jackson's trilogy really brought the story to a much wider audience and made them feel a lot more mature. A film like A Miracle on 34th Street didn't necessarily need a tech-update, but it's a fun story for kids who may not have been too excited to watch a black-and-white original.
Other times a remake is made purely to make money off the name recognition and movie-goers tend to see through it. Generally these films wouldn't have benefited from a remake. Horror remakes like Friday the 13th and Nightmare On Elm Street weren't able to generate enough interest to gain a single sequel, let alone the handful of sequels the originals spawned. A CGI blood-splatter doesn't necessarily look "better" than a practical effect.
The biggest argument against remakes is probably the idea of a classic earning the title of "sacred territory". With some films, an unspoken law develops around them and it becomes known in Hollywood that you just don't touch certain movies.
For whatever the reasons may be, these ten movies do not need to be remade. They aren't broken, they don't need to be fixed, and in some cases there wouldn't be any benefits.
10 Ghostbusters (1984)
The gist: Three scientists that dabble in the paranormal discover a hot-bed of paranormal activity is on the way. They design and construct a number of tools and machines to capture and contain various ghosts, poltergeists, and specters; in much the same way as an exterminator would capture and remove various pests and vermin.
Why it can't be remade: The idea was too original. Had Ghostbusters been based on a book, a comic, or cartoon, it might be up for a remake, but Ghostbusters actually spawned all this peripheral material. Dan Aykroyd has talked about a sequel/reboot for over twenty years now and no progress seems to ever be made.
9 Ace Ventura: Pet Detective (1994)
The gist: Ace Ventura is a lover of animals that that has decided to take it to the next level; he runs a private detective agency out of his home that specializes in cases involving animals. When we're first introduced to Ace, he's recovering a lost puppy that results in a high-speed car chase.
Why it can't be remade: While Ace Ventura is by no means a "classic" or even a great film, it just really worked because of Jim Carrey. For some reason his work in the role made everything else seem a little less ridiculous. They've tried to do a "Son of Ace" sequel but it didn't work. If it can't work with a new actor playing a similar character, it won't work with another actor in the original role.
8 The Shining (1980)
The gist: Jack Torrance is a recovering alcoholic who accepts a job as a winter-caretaker for a hotel high in the mountains. He and his family must stay there in seclusion until the weather allows access back to the hotel. A benevolent spirit creeps into Jack's head and he begins to grow violent. Adding to the weirdness, Jack's son has a psychic ability known as "the shining."
Why it can't be remade: Kubrick didn't follow the book very well at all but he did end up making a truly classic film by putting his own mark on the story. Kubrick is the one director that has adapted stories from books that made the viewer completely forget about the source material.
7 The Godfather (1972)
The gist: The head of a renowned crime family has decided it's time to retire. When he movies on, he wants to make sure he organization holds on to the old ways. The Don wants to pass the position on to his son that wants nothing to do with the business. Meanwhile, a drug pusher wants the Don's influence to further his goals.
Why it can't be remade: The Godfather is one of those movies where you will legitimately shock and possibly offend someone if you mention that you've never seen it. A remake could never carry that same weight.
6 The Goonies (1985)
The gist: A group of kids, each with their own unique personality, go on a quest to find the lost treasure of the notorious pirate known as One-eyed Willy. If they fail, their hometown will be turned into a golf-course by greedy developers.
Why it can't be remade: Generally, kid's movies are fair game when it comes to remakes but The Goonies is one of a number of exceptions. There is absolutely nothing a studio could do to make it better. The practical effects worked best for the story so it isn't gaining anything by a tech-update. With the possible exception of Super 8, you'd be hard-pressed to find a group of kids that had so much chemistry together.
5 Citizen Kane (1941)
The gist: On his death bed, Charles Foster Kane utters the word "rosebud". A reporter meets with anyone that was close to Charles Kane to try and piece together what this utterance could have meant. Through a series of flashbacks we see Kane's rise to fame as a newspaper tycoon and his subsequent fall from grace.
Why it can't be remade: Citizen Kane was once considered the greatest movie ever made. Any director that would want to take on a Citizen Kane remake better be darn sure they can make the greatest movie ever made as well. A biopic on William Randolph Hearst, the inspiration for Kane, might be a safer bet.
4 The Rocky Horror Picture Show (1975)
The gist: A couple breaks down in the middle of nowhere and go to the castle of Dr. Frank-N-Furter for help. The Doctor is a transvestite that houses Transylvanian singers and dancers, and even creates his own man. Musical numbers through-out the film encourages audience participation.
Why it can't be remade: When people still go to theaters almost 40 years later (in costume) to see a movie, it's probably safe to say you're dealing with some very sacred territory. Many have talked about a remake but it never seems to actually get off the ground. Since the movie was based on a stage musical anyways, a remake of a movie based on a play seems a little redundant.
3 Casablanca (1942)
The gist: Rick is an expatriate and club owner in Africa during World War II. One day the ex-love of his life walks into his place with a request: She wants Rick to help her husband, resistance leader against the Nazis, escape the city of Casablanca so he can continue the fight. Rick is torn between doing the right thing and sending his former lover off with another man.
Why it can't be remade: Remaking Casablanca would be silly for a couple reasons. The first is that it's a pretty straight forward story that requires little special effects. Updating the film because new technology is available would be unnecessary. Second, it would be tough to find an actor that would make a claim at being better than Bogart.
2 Indiana Jones (any of them)
The gist: A Professor of Archaeology goes on adventures to uncover legendary artifacts that include the Ark of the Covenant, a set of magical stones, and the Holy Grail. Occasionally, Nazis get in his way as they try to seek the same items.
Why it can't be remade: Indiana is one of the most revered characters in cinema. Most people aren't going to be able to shake the idea of anyone other than Harrison Ford in the role. Since the character of Indiana is based on characters from 1930's serials, anyone wanting to make a similar adventure film could start from there and just make their own.
1 It's A Wonderful Life (1946)
The gist: Thanks to a guardian Angel named Charlie, George Bailey is given the opportunity to see what life would be like for his loved ones if he had never been born - just before he decides to commit suicide.
Why it can't be remade: Like Casablanca and Citizen Kane, there just isn't much reason to. A tech update wouldn't add any value to the movie and the story itself is timeless; telling the story in color wouldn't make it any better. The film is also synonymous with Christmas. Much like A Christmas Story, you can count on it every year around the same time and you'll always find yourself watching it. Some things just need to remain sacred.