Best Film Soundtrack/Theme

I'd say Requiem for a Dream.

That's what I was going to say originally but the only song I remember from the whole movie is the same song they use through the whole thing. While it's an awesome song, I'm not sure if I'd be able to say it's the best soundtrack, since that's the only song in it.

That one song from Saw was pretty awesome too, but I wouldn't say Saw's soundtrack was awesome. The song I'm talking about: