not at all.
FEAR series has a dedicated following most of which are on the PC.
I will bet you any money that FEAR 2 on PC+PS3+360 outsells Killzone 2...on ps3 only obviously so its not a big achievement...
Nevertheless FEAR 2 willl do just fine.
I am getting it day 1
Edit - Review scores will have a big say in Killzone 2's fate. But both games should do fine if they rate 85+