Hands-down, absolutely and without any hesitation whatsoever is Betrayal at Krondor's soundtrack. It's majestically epic, and isn't just a great tune or two, but has a *minimum* of 20 fantastic spellbinding tracks, and lots of variations on a couple of the main theme tracks. Unapparelled.

In a distant, distaaaaant second and third would come Castlevania Symphony of the Night and THPSII. Megaman II and III also had great soundtracks. Fallout New Vegas has a very moody, memorable soundtrack as well.
Ocarina of Time has an obviously fantastic soundtrack as well, as does Chronotrigger.