Mine is Shadow of Mordor.
First game that's kinda felt like it's 8th gen material. Really liked the captain system in it, feel like it's something quite news, even if much of the game was sort of Assassins Creed meets Arknam. I'd like to see more of it in future games. Felt it did quite well with the lore of Middle Earth too, where other LotR titles I've played (Third Age being the largest offender) have been pretty fast and loose with the lore.
Shadow of Mordor was pretty damn pretty, fun to play, felt like it had nice pacing between areas despite the relatively small two maps. Never really got tired with them, and then there's the collectibles and side missions which weren't massively laborious to go through, though somewhat unnecessary for the most part. Also the Branding stuff was pretty fucking sweet, and playing with the structure of the army to get your guy up near the top. Having different enemies with the different strengths n weaknesses and planning around it really helped add variety, and yeah it's all fairly procedural but you didn't mind.
So yeah, my GOTY cos I'd like to see more of it applied to other games, kinda hoping other studios were paying attention. Hoping we don't get a direct sequel though.
Other games I've done this year being:
Ciov:BE, Watch_Dogs (which I feel was a bit rough around the edges, still quite grounded in Ubisofts AC system of game mechanics, but will likely be pretty damn sweet come the second one much like how they did with Far Cry n AC), Monument Valley which was a pretty looking game, though pretty short (it'd be even shorter if not for the overly long animations), and Thief which I never finished. Oh n Pokemone Alpha Sapphire,which I'm still working my way through and while a delight for myself, not feeling quite GOTY stuff.