I'm going to say Red Dead Redemption. I went into the game blindly off of a recommendation of an assistant manager at my job. I bought it on release day, and was not at all disappointed. It's a game that I easily put 40+ hours just into the campaign. When I bought the game I had hernia repair surgery about 2 days later, this forced me to have 2 weeks off of work to recover. I probably played that game for 3 or more hours a day in those two weeks. The game has everything that I constantly am hoping for in a game. Gameplay that mates with an amazing story/campaign, ingenuity, originality, everything that modern games LACK is here. I have 100% completed the game and have touched multiplayer maybe twice. From the ambient challenges, to the stranger missions, it is never a same playthrough. The replay value is so amazing, and the game is so fluid. I loved every bit of it and I am a VERY critical gamer, most games tick me off with their garbage stories, constantly cliche gameplay, and retarded characters. The game hits every note, comical characters, in depth story, and originality. This game comes in an extreme close second to the Bioshock series to me, pick it up, you won't be disappointed.
I had a pretty indepth reply i made earlier, but the server was "too busy" and cleared everything I had, so I had to retype it all.