I haven't played COD since MW2, but am itching for a fix of some console FPS action, and it's pretty obvious Call of Duty is generally the first choice. But I've heard many bad things like how people will send you sincere death threats (see article of attempted murder by an old man) for merely playing better, and due to the game's immense player base, there are hackers that will try to hack your account if they simply feel like it.
Also currently not sure between Black Ops 2 or Ghosts if anyone can give feedback on that as well. Again, please understand my train of thought right now, and take into consideration that I currently don't have a gaming PC.