VALVe's brilliant expansion on it's Zombie FPS series.
Story - 8/10
(IMO) No zombie game needs a good story, you just need a simplistic basis for a plot and likeable characters. Left4Dead 2 has both of these, and like any VALVe game, you'll find yourself laughing at the conversations that take place between the well developed characters.
Gameplay - 10/10
One of the best zombie games of all time. The special infected work together brilliantly, with the new Spitter, Jockey, and Charger additions. The new guns are a blast to use, and the melee weapons adds a brand new way to play. The maps are awesome, not only for campaign, but for any mode. Scavange proves to be one of the best new features, purely because of how fast-paced and addicting it is.
Re-Playability - 10/10
VALVe has released around 3 add-ons, and even without them I'd still be playing it. And with the add-ons you get a new Mutation mode every week to freshen things up a bit.
Graphics/Sound - 10/10
For the first hours of gameplay, you will be awestruck by the pure awesomeness of the zombie gore flying at you. The graphics are amazing, and the attention to detail keeps your eyes glued to the screen.
Great sound effects and hillarious, excellent voice acting.
Uniqueness - 10/10
(Other than the original) there nothing else like it. Slaughtering waves of zombies while you get to objectives has never been this fun.
Anyone who loves a great zombie game should get this. Anyone who loves VALVe should get this. And anyone who loves gaming as a whole should definitely get this.