I agree with Madmick (at least I think I do).
I understand that the open poll of IMDB is going to rate movies differently than a poll of a list of "experts" such as sight and sound. Many people are going to say that the experts list is a more authoritarian list.
But, I don't buy that just because you are an expert on films makes you any more qualified to tell everyone else what a good movie is. Enjoying a movie is close to if not completely 100% subjective. Same thing could be said for music or literature. What makes an expert's opinion of a movie inherently better than my own? Yes, I realize an expert is going to know and understand the technical aspects that may be lost on me...but so what? If a small aspect is lost on me, why does it matter?
If the list of experts don't care for X movie but I do, I'm going to be told my opinion doesn't matter because I'm not an expert. Well, if that isn't a classic appeal to authority, I don't know what is. Experts opinions aren't right just because they're experts. An expert may be able to say that X was done a certain way because of a director's style, and I can reasonably assume he's right because he's the expert. But when the expert says X is good or bad, which is a value judgement, the only backup to that is because he's an expert. What if I become an expert, take all the classes, watch all the movies, even make a movie or three, and I still like X when the experts don't? Am I still wrong?
This is part of the reason why I don't like the notion that kids should be taught "the classics" because they're good books. Teaching 1984 because it has some historical references and teaches kids about some technical aspects of literature is fine. Teaching 1984 because "it's a good book" is stupid, because that's subjective (although I liked 1984 alright).
The only issue I take with using IMDB's poll is it's probably not a great sample of the population. But, the general idea of it makes sense. It's not necessarily to say that Shawshank is the best movie, but it's the movie that people like the most. Just because people like it doesn't mean you're going to.
/rant