Still my statement, and pretty sure "scary" is one of the core aspects of Horror so.
There's a million examples of things that are horror, but aren't scary that people are already naming.
Besides, if I don't find something scary does that make it no longer horror? You don't find Doom 3 or Dead Space scary so you say they're not horror. I don't find Siren scary, does that mean it's not horror either? By your logic the answer is yes.
Fry Cry 3 when you get randomly attacked by gators / crocs whatever
Tomb Raider is pretty damn evil and creepy, although not that scary
First Dead Space was scary, but thats not what kept me from playing it
I gotta say DOOM BFG is the scariest Ive played in a long time. That game just doesn't give you a break, traps galore and it eventually doesnt surprise you, but it still startles the fact that theres DEMONS IN YOUR FACE OUTTA NOWHERE