Shooter
Of the nominees I've only played CoD: Ghosts, Bioshock and Battlefield 4.
Out of those, Bioshock was a decent game with awesome setpieces and story. Ghosts probably has the larger replay value, not single-player mind you, but rather the multiplayer functions are pretty well done. BF4 is just atrocious and rushed. So for my dollar I'm gonna have to say Bioshock if only for the atmosphere and story. Gameplay-wise though Ghosts has it beat hands down, more fluidity and polish and replay value. I didn't play Metro so I can't give it a vote. Sorry.
Platformer
Hands down the Ducktales: Remastered remake is by far my favorite both because of nostalgia factor and its fun through and through. Easy choice for me.
RPG
I haven't played any except Path of Exile and the game is just... meh. Not worthy of any trophy. So I'll pass on voting but guess that out of them either Fire Emblem or Pokemon are cream of the crop. Was it really that lax on RPG's this year? Seriously?
Strategy
Also again don't own and haven't played any of the titles but I'd garner that X-COM's entry is the better of the choices only because I don't see what the Civ expansion brings to the table that would catapult it above the others and I'm still of the mind that the Starcraft II series is just a glorified xpac and graphical overhaul of the original. I loved the original SC, but just can't get behind SCII.
Action-Adventure
Between GTA V and ACIV I can't decide. Saints Row was good but not good enough, and I'm not that into TLoU like some folk are on this site, though I'll say its definitely more a GotY contender than Papers, Please (yeah I went there). So its a tie for me on GTA V and ACIV, both of which have brought me equal joy and pleasure.
Adventure
Well, having said my piece about Papers, Please, and not having played the other picks, I'd still have to say that Telltale is dominating the straight up Adventure market, harkening back in my mind to the Sierra days. So I do hope they get the nod for Wolf Among Us.
Horror
I'm not a horror fan usually, and this year none of the titles released sparked any interest so I can't rightly make a choice. Category, thy name is "Skip".
Well thats my thoughts... and personal GotY out of all the choices?
GTA V because I just feel its a game I can put in any time I want and get loads of entertainment from it without having to bother with story or anything. Its not too over the top, the world is very well put together and feels alive and just generally does me a solid without angering or frustrating the fuck out of me at all.
Thats all folks (credit to Mel Blanc, may he rest in peace).
EDIT: Also why no love for Ni No Kuni, Luigi's Mansion 2, Monaco, Payday 2 (which totally deserves at least an honorable mention), or Tearaway.
All of those deserve to be on their respective genre's list.