Final Fantasy X
Probably my favorite soundtrack of any ps2 game as well!
Super Robot Taisen Alpha 3 would probably be my favorite, it pretty much was the game that inspired me to actually start learning Japanese. That and I've definitely played through the game over twenty times at this point...and it's a 60+ hour game even if you skip the text and all battle animations. >_>
This was one of my favorite ps2 games and needs a hd remaster