Super Mario 3D World for its great platforming and fun levels, though multiplayer can be frustrating in some levels.
Rayman Legends for levels that use up the Wii U Gamepad very well, and the music levels.
Pikmin 3 because I like Pikmin, put about 47 good hours into this game, trying to earn platinum on all those challenge levels.

Mario Kart is gonna top everything on my favs list.

All the games are good but Lego city Undercover just because it differentiates itself from past Lego games.

Although the other games are really good and get very close to winning so far it seems too liked for what it is.

Waiting to see if Smash, Bayo 2, and X take the number one spot.

Super Mario 3D World

Hmmm.... My favorite? I have so many games for Wii U and enjoy quite a few, choosing just one is kind of hard to do.

My most played games would be MH3U and Black Ops 2 but I don't really consider them my favorites.

My favorite exclusive would be Lego City Undercover, I would love to see a sequel to that.

My favorite 3rd party would be Splinter Cell Blacklist, I love stealth games.

My favorite Indie would be Unepic, awesome 2D action rpg

I'm pretty sure I am going to like MK8 more than most if not all my games though.

Either Tropical Freeze or Pikmin 3...
I must add that I'm disappointed at the lack of love for Lego City...

Wonderful 101

I think it's less than a lack of love just an overabundance of love for Nintendo.

Pikmin 3! It's basically the reason I bought a Wii U at launch. I've lost count of how many times I've played through it.

Super Mario 3D World i suppose.

Rayman Legends hands down. Tropical Freeze is a close second. The Wind Waker was also fun since I haven't played it before, and Pikmin 3 felt very atmospheric.

But Rayman is my favourite.