You really need to compare the games in motion to get an accurate picture.
Specifically, Killzone 2 displays at a hardlocked 30 FPS with some framerate drops at 1280x720 with quincunx AA (about the equivalent of 2x MSAA, except with motion blur). Even the first Crysis can easily display at >30 FPS w/4X MSAA at, say, 1680x1050 on a modern mid-range gaming system. That'll look a helluva lot better than KZ2.
Seriously, the PS3 is running like three-generations-old graphical hardware. There's no chance at all that a PS3 game can look as good as modern graphically intensive PC titles, especially in the near future with DX11 games featuring heavy tessellation effects on the horizon (something which the PS360's DX9-era hardware could never dream of).
EDIT: Long since beaten, but it bears repeating because some people can't seem to understand it.
"'Casual games' are something the 'Game Industry' invented to explain away the Wii success instead of actually listening or looking at what Nintendo did. There is no 'casual strategy' from Nintendo. 'Accessible strategy', yes, but ‘casual gamers’ is just the 'Game Industry''s polite way of saying what they feel: 'retarded gamers'."
-Sean Malstrom
