Back on topic: I play it because I like it! I could be playing Crysis 2, but Crysis 3 feels more polished and I like Spears a lot. And I have only played Crysis 3 MP for 16 h, not long enough to get bored or annoyed
In fact Crysis 2 and 3 are the only MP games I play. I tested COD:BO2 this weekend (it was free) and it's OK, but I prefer Crysis 2/3, I feel too limited without a nanosuit