To get back on topic;
I think Columns (Genesis), M.U.S.H.A. (Genesis), and Dark Wizard (Sega CD) are ones I love that haven't already been mentioned. As budgets and AAA titles come about, music gets better and better IMO. Alot of big companies are devoting alot more resources to filling that aspect of their game quite nicely. I thought Too Human (x360) had some good music and I am pretty sure Mass Effect (x360) does as well. Also Gates of Thunder (Turbo Duo/CD) had a great soundtrack.
LOL at Demon of the moor for being an Opeth Fan saying a games music was too metally, LOL