I say keep it just because it's a lot of fun. The story doesn't make sense and the dialog is awful, but the game itself is rather enjoyable. Despite how long it's been out and how much everyone seems to hate it, there are usually at least a few people online each night. I have yet to go a night without seeing other people online. Mind you, I don't play every night, but I've sunk a lot of hours into this game (more than any other shooter). It's fun even if you have to play by yourself, but the AI is a bit on the retarded side, so it's definitely more fun if you have at least one person to play against
Of course, this is all just one person's opinion. I've been told that I'm crazy for liking this game so much. I think people are just being overly picky.