Valkyrie Profile, hands down. Challenging but never frustrating, packed to the hilt with secrets (Seraphic Gate!), fun battle system, and most importantly, a BRILLIANT story. Every single back-story for the Einherjar you recruit was absolutely heart-wrenching.
Resident Evil is a close second, if only because it was the very first PS1 game I ever played, and was the start of my continuing obsession with all things zombie-related.
Resident Evil is a close second, if only because it was the very first PS1 game I ever played, and was the start of my continuing obsession with all things zombie-related.