Since this is turning into a Williams vs Zimmer thread, I see that they do two different things.
Williams is great, but I've always felt that he composes to basically just get his shyt off. The music is good, and I've found that I associate the songs with the movies more because I really liked those movies. Doesn't make the music any worse, though.
Zimmer, at least from my view, makes music that's intended to be played with the scenes he's scoring, since they enhance the film. Inception and The Dark Knight for example, are great movies, but part of the sense of tension and dread comes from the score that plays with the scenes. The opening bank robbery and penthouse robbery of The Dark Knight aren't anywhere near as intense without that droning, building noise played as part of the score, for example.
But to each their own. That's the beauty of music.
