Hm.........Castlevania Circle of the moon first level "Catatomb", Aria of sorrow "the last part a little before Dracula and most of both Metroid's game music were good.
I usually don't listen to the music while I'm playing gba (the lack of a headphones jack really annoys me) but I always went out of my way to listen to Golden Sun's music. It's track was almost worthy of a console.
[quote author=Grim Reaper link=topic=21015.msg114879#msg114879 date=1132496634]
The music in Megaman Zero 4 was awsome and was the best of the whole series.
[/quote]
you said it all.