Interesting discussion thus far. One thing I never mentioned in the OP is age. I believe if you saw Star Wars at the theaters in 1977, and it blew you away, it will always be your favorite. I'm not saying this is the case with everyone, but I have uncles and cousins who saw the film during it's theatrical run, and were completely blown away, and as far as they are concerned no Star Wars sequel or prequel can ever top that experience. On the other hand, if you didn't see Star Wars in 1977, and don't have that nostalgic attachment to it, perhaps you judge the films on which one gave you the most enjoyment. I'm not saying this is the case for everyone, but I've noticed that most people between the ages of 18-25, who have no nostalgic attachment to the 1977 film at all, generally prefer Empire. Also, that particular age bracket is the one that votes the most on IMDb, which can perhaps somewhat explain Empire's higher ranking.