My vote goes to Shadow of the Colossus. That game was nearly flawless and easily my favorite on the system. I love games that can tell a beautiful story without using many words. That's hard to pull off. If it just had a PC's power to fuel a 60fps frame rate, and high resolution to see the individual hairs on those huge furry bastards, I'd probably die on the spot.
Like this faked press shot. Ignore the shadow problem with the horse:
