11 Fallout 3
Bethesda's Fallout 3 presented players with a truly unique concept: the ability to play the game more-or-less however they wanted, allowing for the game itself to play out in an almost infinite number of ways. Sure, this was done before with games like Grand Theft Auto, but never on this scale. You can play Fallout 3 conservatively, carrying out sidequests and trying your hardest to make the best decisions possible. Conversely, if you're in a particularly diabolical mood, you can just run around like a maniac, blowing away everyone you come across, be they good or evil, man or animal. Of course, massacring everyone you meet in the game comes with its price, such as receiving negative karma points and ultimately altering the ending of the game. If you own a next-gen console, do yourself a favor a take this gripping Xbox 360 game for a ride.