OK, I know I'm a wee bit late to the fight but:
Gears of War 2 vs. Killzone 2: TIE. I've played both thoroughly and they each have areas where they are stronger than eachother.
Killzone 2 vs. CoD: WaW : killzone 2, by a very slim margin. The graphics are better and, this is just me, the shooting is better. But WaW is still a great game.
Killzone 2 vs. Resistance 2: Killzone 2 but not by much. Resistance had great multiplayer, but Killzone's single player was better, and it's multiplayer was good too. Resistance is still a quality game.
This is all my opinion, and they are all great games.
I know it is late but i think I've had enough time to decide:
Killzone 2 vs gears of war 2: Gears of war 2 more varied options badass chainsaw superior cover horde mode is a pure thrill the list goes on and on no contest gears of war 2
Killzone 2 vs resistence 2: tied where killzone has realisam awsome detailed graphics superior plot but resistence 2 is about the spectacle step out to see ruined chicage force some rockets down a giants mouth it's all good and they both have strong multiplayer.
Killzone 2 vs call of duty world at war: killzone 2 world at war is basicly world war 2 call of duty 4 true tweeks were made to the impeccable formula but killzone has fresh ne scent to it world at wars tries and falls
extra game
Killzone 2 vs l4d: l4d tough one in the end i gave to l4d because well im valve fanboy there is plenty to do in only 4 campaigns i want to do it again and again and again.
2007 shooters
Killzone 2 vs halo 3: tie same argumant as resistence 2 the spectacle the awe of relentless hordes in halo 3 its all good
Killzone 2 vs call of duty 4: call of duty 4 its another tough one killzone 2 lost because it didn't anything new
Killzone 2 vs the orange box: do i realy need to say? the orange box enough said.
play what you like. Both have there pros n cons, but they are totally different games with different themes. Ive have COD WAW, stinks!! would rather play COD3.Anywho, I'm just waiting for M.A.G.!!!
these games are all different. they are fps and thats all they have in common. they were made for different consoles, engines, companys, and types of gamers. they werent made to be compared because half of them didnt even come out the same year as kz2. to compare them is like saying a hotdog is a hamburger, only with different condiments. good article, of course. ive come to expect nothing but the best from gamesradar. but still. i love all of these games, but they all have different purposes to the stories. cod:waw is wwII, which,honestly, is getting old. gears 2 is facing large numbers of enemies and finishing them off with sattelites (very fun :D). resistance 2, well, alien invaders on earth. again. earth is unlucky. aliens need to leave us alone! this is a good game still, but aliens? wow. on earth? big surprise. but kz2 is where humans who left earth long ago atacked one of earths colonies and nearly defeated it, only to be turned back at the brink of victory. you then mass an army of survivors and attempt a last-ditch effort at destroying their world. by the way i realise this comment was very long. sorry about that. i get carried away. there i go doing it again.