Silent Hill for the Ps1. It was one of those games where it's scariness wasnt in making a big monster jump out at you around the corner. It was a game where the subtle ambience of something lurking outside, and the eerie camera made it truly scary.

Tomb Raider 1. Though not scary in the sense you guys are talking about, it was scary in its own way. The black fog that was there to hide the draw distance, the loneliness of being hundereds of feet underground in a hidden cavern, the absense of ambient music...

and the first time you see the T-Rex barrel down the hidden valley from the black fog. Im glad they chose to not give him an intro cut scene, because he literally came out of nowhere. It was fantastic.