Hrm the three most scary games I have played would be
Eye of the beholder, the creeping noises of monsters are frightening
Resident Evil series, Somethimes you jump like a sissy playing that game.
ALiens V's Predator 2, Damn thats one scary game when your in the dark tunnels just waiting for an alien or something to attack. the old scanner pulsing makes the scare even worse. Blip Blip Blip De De De Slash Arrrr.... every step is a fright.