I'm sure you've heard of Nobuo Uematsu Motoi Sakuraba is one of my favourites too, having done stuff in Star Ocean games and most of the Tales of series, as well as others I suppose Kajiura Yuki could count as a good one too having done Xenosaga 2 (maybe others, can't remember off the top of my head), although she's done more anime soundtracks than game stuff