Simple, what are your favorite games from each year dating back however long you have been gaming? The only rule is the game can only be applied to the year it came out. If it came out in 2014 and you played it this year, it is still a 2014 game.
For me...
2016: TBD. Partially because I have been too busy to really commit to any game, but nothing has stuck out for me. Battlefield I and Gears of War 4 are two really good games, and if I had to choose I guess I would say Battlefield is my favorite game to come out this year. However, I have Final Fantasy 15 and Watch Dogs 2 (which I have heard a lot of really great things about so far) sitting on my shelf and that could change things. Not to mention The Walking Dead Season 3 will be out in a couple of weeks and I might give Dishonored 2 a go one of these days.
2015: The Witcher 3. Not even a question. The Witcher 3 is the best single player game I have ever played. Shout-out to Metal Gear Solid V: Phantom Pain and Dying Light.
2014: Destiny. 2014 was a terrible year for gaming IMO. This was after the X1 and PS4 had just came out and it was just an empty year for gaming. Destiny benefits from all the expansion packs they released down the road. At launch, this was a game with so much potential but no content. While I strongly disagree with their DLC approach rather than including it with the game, I can't lie and say I didn't end up loving the game. The House of Wolves DLC adding Trials of Osiris made this one of the best games of 2015 Summer. Honorable mention to Alien Isolation.
2013: The Last of Us and The Wolf Among Us. This year was excellent. The Last of Us, The Wolf Among Us, Tomb Raider, Bioshock Infinite, Walking Dead Season 2, Splinter Cell, Battlefield 4, AC: Black Flag (which, compared to the other recently released ACs, was really good I thought), Arkham Orgins, Dead Space, State of Decay. Ultimately I couldn't choose between The Last of Us and Wolf Among Us. The Last of Us obviously had the better gameplay and the story was strong, but Wolf Among Us was an amazing experience. I wish they would do a sequel, but it isn't looking promising.
2012: The Walking Deadon (Season 1). Perfect. Honorable mention to Black Ops 2, which is one of the most underrated games ever.
2011: Batman: Arkham City. Holiday 2011.
2010: Red Dead Redemption. One hell of a game that still plays great. Probably still in my top five.
Other:
2009 - Uncharted 2
2008 - Fallout 3