I think this is a good thread, because Killzone2 has seemingly been forgotten, or at least there seems to be a certain amount of people that want it to be, the game is AAA yet often not treated as one. You hear everyone saying U2 looks better, but the reality is in some ways it does, but in other ways Killzone2 is besting it, particularly in lighting and animations(with death animations particularly more impressive, but U2's animation blending on the character looks better.) KZ2 has a more mutted art pallet, but better art direction(I can't think of another game that matches KZ's art direction, outside of star wars) U2 has more detailed character models, prettier textures, and much more vibrant colors.
Any ways both games are outstanding, U2 is getting the credit, KZ2 isn't (part of me thinks, that this is because certain people think one game is a threat the other isn't).
I do understand if you go from playing one of the CoD games for 2 hours then pop in KZ2, the game might seem to chug along and feel slower - it kind of is done injustice when these people drop the game immediately before taking in just what it has to offer, and just how impressive the graphics really are. The music is great, the story is actually good. Turn out the lights, adjust the game lighting, and use surround sound and this thing is a real treat.