Should I buy Uncharted 2 or Killzone 2?

I have the money but I can only buy one. I'm probably going to end up buying both but I want to know which one to buy first. I heard Uncharted has really good singleplayer and Killzone has a really good multiplayer. What I'm looking for is balance between the two. I don't want a singleplayer only or multiplayer only game. Which should I get? I'm a big fan of the Call of duty series, so would I like KIllzone 2 better? Also, which has a bigger online community because I don't want to buy a game that nobody's playing.