John Barry has done some that are at least equal to the movies he was scoring and in other cases superior to the films he was scoring... Somewhere in Time, An Indecent Proposal, Walkabout, Born Free, and Frances all come to mind as exceptional scores.
Ennio Morricone has also done some brilliant film scores most of which have been for Sergio Leone (all those spaghetti westerns) and Ennio Morricone (best known for Cinema Paradiso).
And there's a moving bit in Love Actually by Craig Armstrong called Glasgow Love Theme or something like that.
Gotta add Danny Elfman and Mark Isham to that list, and BITD, Vangelis; all pretty prolific at different times/movies.
It's too bad you can't always get the score...yeah, usually a soundtrack, but they don't always release a score. What's even more annoying is when they use a song in the trailer...and it's not in the movie...it's just a teaser track for the trailer...OY. No, "O Fortuna" from "Carmina Burana" isn't in that movie...but it looks like it COULD BE...heh.