I guess the problem with high scores on imdb is that a film could have a high rating because it has a devoted fan base and/or has been released recently therefore more votes etc. Although obscure films tend to do quite well in the ratings too because the people that tend to watch them are fans of that particular genre.
For me personally, The Matrix has got to be up there in most overated films, think Kill Bill should be up there too, I like Tarantino films, but this one got a little bit too much praise.
Oh and the first Lord of the Rings!!! I was so miserable by the end of it, and there seemed to be so many potential endings and then it would go onto another scene, made me want to cry!