Overrated:
300 - Fucking terrible movie.
Sin City - Gawd.
Napoleon Dynamite - This was an okay movie. But all the stupid teenagers spouting out all the quotes from the movie when it first came out got really fucking annoying, fast.
Forrest Gump - I hate putting it here, because I love it so much. But people talk like it's the greatest movie ever made, and frankly they're are many better movies than this one. Pulp Fiction should have won Best Picture in 1994.
The Notebook - Like this movie a lot too, but again the dumb girls that think this is the be all, end all of film because it's a good love story. Shame. Casablanca and Purple Rose of Cairo (though the latter is a different kind) is where the good love stories are.
Underrated:
Reservoir Dogs - Tarantino laid the ground work for his future films here, including the great Pulp Fiction. Should be talked about more.
Citizen Kane - I know it's considered the greatest film of all-time critically. But does anyone besides me and 60 year-old, hard-nosed critics really enjoy this film?
Predator - This movie's special effects make Alien look like child's play. While the latter film has aged quite significantly, Predator looks way ahead of it's time. You would think the alien gadgetry, explosions, and the Predator costume would look cheesy by now. It doesn't. It still holds up amazingly well today. The atmosphere is really what makes this movie, and again it holds up.
Good Will Hunting - Sorry guys, the script is fantastic.
American Graffiti - How come George Lucas' best directorial movie never gets talked about? (Right, because of Star Wars, I know.)
Empire Strikes Back - People take this one for granted because it's a Star Wars movie. Doesn't matter. Everything about this movie is phenomenal.
I could go on, but it's late.