One of the greatest films ever? I don't think that's an understatement, and I'm not just saying it cause I'm a Bill Murray fan and he happens to be in it. Granted, he brings to the movie his usual subtle quirkiness, but that humor isn't out of line with the general mood of the film. The whole thing is seriously funny and somehow seriously real, but at the same time doesn't always take itself seriously. Seriously. The idea of the movie doesn't come off sounding like a very captivating plot: high school geek and middle-aged millionaire fall in love with the same first grade teacher. Not exactly material for a high-grossing box office hit. But I don't think plot necessarily matters when it comes to making a quality film. It has a fantastic script, believable character development, and top-notch acting, and that's what counts in making a memorable film. Why do we love Rushmore? Max and Mr. Blume are the same person, Mr. Blume is just older and wealthier. They are both creative, romantic characters whose motives are ultimately selfish. My guess is if you appreciate this film, it's probably because you're the same way. This movie is about us. We are the boys who do everything we want to and nothing we're supposed to. The ones who go to college and get by on as little effort as possible, but somehow still pull through. At one point or another we all believed we could make our fantasies a reality, and watching this film makes us optimistic about those things again.
Also, I don't think a soundtrack makes a film, but it can certainly help set the mood. Yes, I have to agree with the other commenters for Rushmore: great soundtrack. But you already know that and it's been said a hundred times, so I think I'll just leave it at that and not beat it into the ground any more than it already has.
Right. Good movie, watch it if you haven't yet.