ZombiU Bayonetta 2* Captain Toad: Treasure Tracker Mario Kart 8* Super Mario 3D World Donkey Kong Country: Tropical Freeze* New Super Luigi U The Legend of Zelda: Breath of the Wild* Rayman Legends* Splatoon Super Mario Maker
The ones with a * were ported to Switch, so if you plan to get one maybe you'd rather wait and play them there instead.
Captain Toad: Treasure Tracker - Surprisingly fun little puzzle game with lots of replay value if you're a completionist. Donkey Kong Country: Tropical Freeze - Better than the first Returns game. Mario Kart 8 - The best Mario Kart game ever, it's amazing. New Super Mario Bros. U - The best NSMB game. New Super Luigi U - Different, but challenging and fun. Splatoon - Surprisingly addictive shooter. Single player is pretty lacking though, and I doubt the online community is very strong now that Splatoon 2 is out. Super Mario 3D World - Excellent linear 3D Mario game, with optional multiplayer. Super Mario Maker - Both making and playing levels quickly becomes addicting. Super Smash Bros. - I'm not a Smash pro but I thought it was pretty good. The Legend of Zelda: The Wind Waker HD - The definitive version. The Legend of Zelda: Twilight Princess HD - The definitive version. Yoshi's Woolly World - Extremely fun and charming platformer that makes collecting a joy.
King of the Zombies mode in ZombiU is actually really fun and a great use of the gamepad. You can drop zombies of different types on the map while the other player has to survive and claim flags. It's very good asymmetrical gameplay.