STALKER isn't a horror game. If it was a horror game, much of it would have to be scripted, like FEAR, to be scary.
Well, S.T.A.L.K.E.R does evoke a bit of horror in its own way, with an eerie atmosphere akin to a "ghost town", all those howling and wailing ambient sounds in the background, the darkened corridors of subterranean facilities, those vile mutants... coupled with the gameplay complexity, I LOVE IT!
On another note, if and when GSC completely falls apart, I hope some other company can just buy the rights to the intellectual properties of the S.T.A.L.K.E.R franchise and continue on the legacy... if that were possible.
Sigh... reminds me of what happened to the Homeworld series... T_T