Oh man, where to begin.
It can't just be one game...
Drive Club - sure it had technical issues, but this was the purest resurrection of PGR I've played to date. The handling, the track design, the visuals, it's all pure PGR. It's just so very refreshing to see a game not afraid of trying to be a classic circuit/track racer and not feel forced to try and conform to what might be considered genre norms.
Sunset Overdrive - Incredible game, traversal was right up there with Jet Set Radio, amazingly well designed world, extremely fun and engaging gameplay that never gets boring. So good.
D4 - Swery delivers yet another wonderful treat. Story is superb, voice acting is on point, dialogue is incredible, Kinect controls actually worked. It's the game Telltale's have been trying to make for the past five years and Swery knocks it out of the park on his first attempt.
Wolfenstein - What's not to love? Wonderfully told story, interesting characters, fantastic gameplay, orgasmic gunplay and it didn't need to rely on any gimmicks. It doesn't try to be anything more than it is, a pure first person shooter and that quality shines through in spades.
Velocity 2X - Not much to say other than I love the new platforming sections. Was a little worried it would be too samey, but it not only managed to feel fresh, it exceeded every single one of my expectations.
Shadows of Mordor - The nemesis system .Does any more need to be said? Not only did it deliver, it damn well set a new standard for open world games. It's going to be hard playing a similar open world game and it not featuring this amazing and dare I say, revolutionary game system.
Alien Isolation - it's rare to come across a game where the hype is actually matched by the end product, but this game right here manages to do exactly that. It's by the far the best representation of an Alien in game since AvP2 almost 15 years ago. The atmosphere, the sound, the gameplay, it's dripping in fear.
Bayonetta 2 - I really shouldn't be adding this as I haven't played more than an hour, but holy shit, what an hour. You sometimes worry that a game will feel too samey and not really feel fresh, but that doesn't apply here at all. Platinum knocked it out of the park based on my hour of gameplay and I can only imagine how much better it gets.
There are so many more, but these are the main ones for me. The ones that instantly come to mind when I think of which games lived up their respective hype.