Come on, Amnesia was the least scariest game I have ever played. Simply said, the protagonist was just hallucinating, going on a PSTD-like state. It wasn't scary for me at all, only on "water" levels like the sewer because I have aquaphobia/hydrophobia.
I also find the way he gets easily scared of darkness silly.
Still trying to find a REAL scary game. That "Afraid of Monsters" mod for HL1 wasn't so bad.
I think the scariest for me was one of the modules for Neverwinter Nights, something called "Zombie Nightmare 2" I guess. It's not just zombies, there were more scarier creatures. Those good ol' times.