One thing I hate about modern films nowadays is ditching proper soundtracks and instead opting for songs. Classics like The Great Escape have their own soundtracks, unlike modern films like Avatar that's soundtrack is a Leona Lewis song. My favourites are probably Jaws or Indiana Jones.
This topic should be in Xcite btw.
I don't think that's necessarily true. Songs have been used in Soundtracks for decades - the 'Best Original Song' category has featured at the Academy Awards since 1934! I don't really see anything wrong with that, when it compliments an original score. Avatar, to my memory, had an original score, just had the Leona track running through the end credits. Besides, wasn't it written purely for the film?
There are too many truly great scores to mention, and indeed, some of the finest and most iconic have already surfaced in this thread. One which hasn't, and has probably become one of the most used pieces of music on television in recent years, is the overture from Requiem For A Dream. A fantastic piece of music.
Sunshine also had an amazing and epic score which complimented the atmosphere of the film brilliantly. I can't help but love some of John Carpenter's own creations too. The simple but effective horror piano pieces in Halloween and The Fog are legendary.
Film soundtracks are such an underrated, yet key part of cinema. I mean, imagine 2001: A Space Oddysey if it'd be set to different music. It just wouldn't work.