The score for Psycho is probably his signature, life achievement. I'm not sure what other piece of movie music has seeped so far into the public consciousness. I mean, 4 repeated notes have become shorthand for everyone to use, even people in conversation. And everyone knows what it means, even, as Eddy says, if they've never seen the movie or further, have no knowledge of the movie whatsoever.
That being said, Herrmann's work is the first time I ever became aware and paid attention to, music in a movie. Usually it was just there.
But in the scores for 7th Voyage, Mysterious Island and Jason, he created something that's as much a part of my childhood as Marvel comics. And that can't just be nostalgia talking. Those scores are brilliant and innovative, evoking mood and movement and action perfectly wedded and even ENHANCING what your were seeing on screen. I think he is unequaled in this. Sure there's other great composers, but throw something out there like, "OK, here we need a Giant Crab song" and no one is going to top what he did or even equal it.
So I can't vote. Best as in objectively "best"? Then, Psycho.
Best as in what I like best? Then,
