I don't really know what kind of PC problems you are having, or maybe problems selecting proper PC components. I recently built a new PC, works out to ~$600-700US that runs Crysis smooth in all but the most intensive parts @ 1900x1200, and at that resolution you don't need any AA to look amazing.
I'm not trying to discredit the PS3 or Killzone 2, but don't try to cover up the obvious things like how Crysis is a 3 year old game that bests Killzone in many areas of graphics.







