1. O Brother
2. Saturday Night Fever
3. Singles
4. The Graduate
O Brother Where Art Thou is bona fide.
SNF and Singles are interesting cases in that each soundtrack crystallized a particular musical genre in the public mind (disco and grunge). Singles is a fun little movie—I’d just as soon watch it in preference to the others, except O Brother—but neither it nor the soundtrack are masterpieces (too much Mudhoney, not enough Westerberg).
Paul Simon’s soundtrack for The Graduate is fine, but the good songs are all on other S&G albums and the instrumental stuff doesn’t really work outside the context of the movie. My ranking here is probably affected by my utter dislike of the film—a smug, self-righteous, pointlessly misogynist and just generally nasty piece of work. imo.
Music primarily composed for film: SNF, Graduate.
Music primarily culled from previous recordings: OBWAT, Singles.
I'll go with schleuse's order. But my favorite soundtracks by various artists are "The Harder They Come" (hello 1972 poll) and "Judgment Night" (Bad movie, great collaborations between rock and rap bands.)
As for great soundtracks, I'm going with Pulp Fiction", "Forrest Gump", and "Goodfellas". All three are incredible movies as it is, but they have soundtracks that are just plain incredible. Especially "Forrest Gump".