It's similar to how you play a offline split-screen game it eats up resources in the game so singleplayer(campaign) looks better while multiplayer(competitive) looks like crap, and the fact there's more than just you playing the game at the time.
Do people still play this? I'm waiting for MoH Warfighter, and I need something different to play until it releases (I've been playing Uncharted 3 since November last year). Is this game dead online or no?
Nope. They're quite a few people still playing this. I play atleast every day or try to. If you decide to get it you can add me and play a few rounds. Also these forums are more active. http://community.killzone.com/t5/English-Forum/ct-