A rehashed game gets a rehashed review, starting with Black Ops 2.
The Campaign is about as generic and uninspired as it gets. Some terrorist group is threatening the lives of millions for whatever reason, and you're squad has to stop them. But let's be real, hardly anyone actually plays the Campaign, since you know, it is so bland and generic.
Multiplayer is essentially the same thing it was in 2009 when Modern Warfare 2 was released, and it will likely be the same until people finally wise up and stop buying COD every year. Oh, I forgot, they added some new weapons and maps and tweaked the perks and killstreaks. It doesn't change the fact that multiplayer is still the same, repetitive, lag-infested experience every year.
Since this is a Treyarch Call of Duty, Zombie mode returns, and, like you might expect, it is pretty much the same thing. You kill Zombies in waves until you all die. It is what it is.
So to sum up, it simply isn't worth paying full price for Black Ops 2, since it is a game that runs on an outdated game engine, with outdated graphics and boring, stagnant gameplay. If you must buy this game, then just be aware that innovation and improvements are practically non-existent in Call of Duty.