I like being able to play on a gamepad while my son or girlfriend uses the Xbox and vice versa. I think the gamepad is pretty neat and has some cool uses in Captain Toad, Super Mario 3d World, and Kirby Rainbow Curse. Drawing and pulling out platforms and blowing windmills to activate bridges were creative uses of the pad.
I love the new Mario Kart also when it doesn't kick me out of a race on the rare occasion I'm leading (this has happened a few times while I'm in first and makes me throw a fit). Also, if you don't want to play it on pc, there's avgn. This game rocks.
Wii U has Captain Toad, Donkey Kong Tropical Freeze, Game and Wario, Hyrule Warriors, Kirby Rainbow Curse, Lego City Undercover, Mario Kart 8, NES Remix Pack, NSMB/NSLB, Nintendo Land, Pikmin 3, Rayman Legends (multiplatform, but the gamepad makes the WiiU version unique), Super Mario 3d World, Super Smash Bros, Tank Tank Tank, and Zombi U. If you're not really into Nintendo exclusives then there's not much reason to get a Wii U. I'm a huge Halo nut, but Halo MCC is a mess so I held off on the Xbone. All of the Wii U games work pretty well out of the box. The ones that do take updates don't take hours like the Xbox1.
It's all about exclusives and what YOU want to play. I like Nintendo and have a 6 year old so for me the WiiU is perfect. I usually don't play a ton of games. I rotate between 3 or 4 I really like, with the odd storymode campaign experience thrown in. Eventually, I'll get a Xbox1 to play Halo and Gears of War, but from what I've read, that system needs some work still before I'd be happy with it.
Edit: there's also Bayonetta 2