i was quite young when i first played doom, just the concept of going to hell scared me shitless. seeing the torsos chained to the wall, also priceless.
next in order would have to be quake 2, first time i really played any fps to any extent.. slasher guys, yelling "TRSSPASSR" at random intervals, had me frantically looking around for where the sound was coming from :P
played RE1 the remake, had never played the first one... goood. buddy of mine and i never played it before 1am.. highlights were encountering the berserkers first time, chasing you down the halls.. there were portions within the house where thered be a dark hallway, and you just KNEW there'd be a zombie there.. hardest thing to force oneself to go down that bloody hallway
and lets not forget the dogs jumping through the windows, my first time through.. god, my heartrate was through the roof
great game, i measure scary on the ability to force myself to go play the damn game again.. if its hard to do so, its scary