Uematsu is amazing, so most of the final fantasy series has something. The music for Chrono Trigger was, however, epic, and not simply the work of Uematsu...
Koji Kondo is as well, hence the Zelda and Metroid series.
Super Mario RPG is up there.
There are MANY games out there with epic content, from Dragon Warrior to Xenosaga to Megaman. Some really stand out; but you can't really say one game has the best.
Final Fantasy has some of the most epic stuff since around FF7 or FF8 not because of the pure musical content, but rather because of the arrangement to the game. They've been getting good at this, games are starting to become more like operas (I hate opera, but whatever).