Drakengard for its craziness and it's one of the better story lines I've seen, not too many games out there that make you play a psycho murderer who's just out there for the blood.
Final Fantasy X, I loved the music and the bittersweet ending (X-2 doesn't exist to me), the characters made me feel very emotionally attached to them and their stories.
Valkyrie Profile: Lenneth needs to be up there too for sure, along with its sequel/ prequel, Valkyrie Profile: Silmeria, both are amazing games with an amazing story and soundtrack.
So for me, it's really a tie between those 4 games. I can't decide!