Ultima: Exodus for NES.
I've got very mixed feelings about it as a game, but I always thought its music had a special sound to it. Enough so that even if I never got around to beating the game, and always got frustrated and gave up halfway though, I kept on just wanting to like it for the music's sake!
(actually, this is the same reason I ever made it through Chrono Cross.... *ducks*)
My favorite track from the whole game would have to be the one just past the title screen: in the menu where you select which save game to load... my brother and I were briefly obsessed with it for a while as kids, and had a weird tradition where we'd sort of doot-doot/hum it in unison at first, then split up with me on melody and him on the bass line. He'd really get into it on his solo! The other really good ones are the town music and the main castle music.