[SPOILER] Requiem reminds me of Amnesia a little bit...

[Googolplex]

Yeah, Requiem has great puzzles. And it is also creepy. The Penumbra atmosphere is creepy by default, you don't need monsters or apecial effects. Just the environments are creepy enough to call it horror.
But except the gameplay, I never found something similar to Amnesia.
And in my opinion, Overture is the best game ever made in Frictional universe.
Overture has the best puzzles, the most oppresive atmosphere, the best story and is the most credible game.
Black Plague was the creepiest, but shorter than Overture, less puzzles, incredible story (the parts in minds) then Clarence talking was destroying the gameplay more and more. Great game also, but not as good as Overture.