Some pretty typical answers up in here... I wonder, do people think certain music is epic, simply because it is orchestrated?
Some of my favorite soundtracks are as follows, but not in any particular order:
Megaman 2
Riven: The sequel to Myst
Myst 3: Exile
Super Castlevania IV - yes, i think it's better than Symphony of the Night. Really, all 'vania music should be on this list.
Otogi 2
Panzer Dragoon Orta
Batman(NES) - this ain't no Danny Elfman PoS
Silent Hill series - notably, games 3 and 4.
Oddworld: Stranger's Wrath - ambience + chill groove + western = amazing
Sonic the Hedgehog 1 and 2 - I always did like Sonic music more than Mario, even though i preferred the Mario games.