Undertale

Out of the one's you listed, i played Xenoblade X, MGS V, Undertale, Splatoon and Super Mario Maker.

My GOTY is Xenoblade Chronicles, followed by Metal Gear Solid V. After that comes Super Mario Maker, Undertale and finally Splatoon. Will play Witcher 3 next year.

About Xenoblade: It is my GOTY because of the huge explorable world and the fun gameplay, especially the battle-system. I always liked the exploring part of open world games but this game easily tops every single one i've played so far in that regard. Of my 105 hours, easily a third was just running around and exploring those beautiful unknown continents of Mira. Sure, the game has more flaws than the other games on the list but i had so much fun with it that i just don't care about those flaws.

After playing Metal Gear Solid 5 in early november, i was seriously afraid that i couldn't enjoy the open world of Xenoblade anymore because of how well it played - for no reason as it seems. At that point, MGS was my top contender because of how incredibly good the game feels to play. I also really liked the cutscenes and parts of the story up until the point where i played (around 30 hours in the game).

Since Splatoon and MP10 are the only games i bought which released this year.
It will be SPLATOON!

I'll go with Splatoon, it was also the surprise success of the year.

Yakuza 5 hands down.

It may be a 2012 game but came out recently for the rest of the world.

Grim Fandango remastered.

For now I'll say Splatoon, but I've only played 8 hours of Xenoblade and I still need to get Witcher 3 and Bloodborne.

MH4U.

The Witcher 3 Wild Hunt.

Rise of the Tomb Raider - Nothing beats Lara's hot sexiness, especially when she is no longer shovelware.