@ Reamus: I strongly have to disagree with you about John Williams. It's true that his work is not anymore what it used to be, but the Soundtrack of Star Wars IV-VI is one of THE masterpieces of film music. Everything has its right timing, pacing etc here. If you listen carefully, the "same chords" etc is no sign of missing inspiration, those are called "themes" and "variations", because that's one of the main points of those soudtracks- characters, locations, they all have their own corresponding themes, which get varied and reprised during all of those movies. It's a sad thing Williams kinda lost that approach for his newer soundtracks.
Other than that:
- Ennio Morricone: Needless to say any more (maybe that there are many great soundtracks for movies that I think are rather unknown in the US, like many Belmondo-movies - LOVE "The Professional")
- Basil Poledouris: For "Conan" alone he deserves a memorial
No one else really comes to mind.