[SamandMax]

Now that Amnesia is out, that's the definitive answer. I've played a lot of horror games in my life and Amnesia is scarier then them all. There's a section in Silent Hill 2 where you have to wander around a labyrinth that I always thought was the scariest thing in any game. Amnesia is literally that scene stretched over an entire game, it's just consistently terrifying from start to finish.