Personally I like co-op very much; though it's sometimes taken into wrong direction these days. Anyway, the lack of co-op is a pity but it's probably not a very important feature in this case (it usually isn't).
Killzone 2 doesn't seem to have anything revolutionary but it's one of the games I'm looking forward to. It's kinda pretty and its multiplayer is class-based, and I like class-based games. Well, at least I like Enemy Territory (and not Battlefield and only maybe, and even then only a little, Team Fortress 2) :P In any case, Killzone 2 might be something I'm getting. I guess I'll wait for the reviews first, though, as I want an unbiased opinion (well, rather a description as reviews aren't to be trusted very much but reviews offer a description).







