Finally, which one is the best : Gears of war 2, Killzone 2 or maybe Halo 3

[xlost7]

I haven't played Killzone 2 yet, so my opinion on the game doesn't really factor into this decision to well. Although I do want Killzone 2, I still think Halo 3 is by far the best out of the three. Reason being co-op story mode and multiplayer online just based my decision!