The music in Star Wars probably deserves about 51% of the credit for this movies success. If the studio had made the decision that “hey, it’s a sci-fi outer space movie. We need some electronic synthesized futuristic music to go along with it” Star Wars may have been a big dud.
The original trailer for Star Wars, that I saw in the theaters in January of 1977, had a non-John Wiliams score to it. It was a sort of brooding repetitive score, and I hated it. (The “Star Wars” logo was different, too – Blue lettering in a different typeface, not the flashy, yellow-outlined logo now in use).
The scenes were all the same, but it didn’t look as interesting or exciting. I saw the original trailer many years later at a con, long after all three original films had come out, and felt the same way.
Watched this recently for the first time in 30 years, and was very struck by the music.
Yeah, but wait until you see the restored, digitally revised, re-edited High Definition Special Edition Original Trailer. It will be released for the first time on HD-DVD in 2009, for the second time in an Expanded Special Ultra High Definition version in 2012, and then in a Final Definitive Collector’s Deluxe Definition Anniversary Edition in 2016. Then it’ll really kick ass.
There’s a related issue I’d like to insert for your consideration. That’s when a movie’s music is so subtle and so underplayed that you don’t even notice it. That’s how Schindler’s List affected me. I remembered only the solo violin at some particularly poignant moment and no other time. When asked what I thought of the music, I asked back, “What music?”
That’s one mark of well-constructed and well-placed music.
The 2001 Ocean’s 11 and Ocean’s 12. The movies themselves are enjoyable light fluff, and it’s the music that really makes them fun to me.
Very familiar with this score – when we used to play ches, a friend used to put this on as background music.
As a side effect, I had George C. Scott’s speech at the start memorized, since it’s on the recording, too. I was surprised to find, years later, that Patton had made a speech very similar to it – I assumed that they’d perhaps used many lines and phrases of Patton’s in coming up with that speech, but not that they were all together in one place.
I wouldn’t. That sounds about perfect. 
The original Dracula
The Day of the Jackal
Sleuth
Twelve Angry Men
Of course, the first two have practically no music, anyway, so it’s not a stretch. The other two are virtually stage plays. (So was Dracula, come to think of it)
The first one I thought of was O Brother, Where Art Thou?