Too scared to play Amnesia

[Googolplex]

Well, I think dead space's(EA game) enemies look scarier than Grunts... Grunts were scary as hell until I saw one from close.

The first Grunt I saw was the one in the Archives at the beginning.
You only can see him very close, he's about 1-2 meters behind you.
And I got scared to the ground.

Dead Spece is not scary because it is action game with "monsters". A Grunt is not a real monster.

Games become scarier when you don't exactly know what horrors are hunting you.

That's not always correct. In general you have right, but if the whole game is about unknown horror, which is realized by strange effects, you got familiar to that very soon. If the horror is all the same again and again, it will be no longer scary.