The sheer number of quality exclusives make it well worth owning.
Right now, my library consists of these games which I can't play anywhere else:
Bayonetta 2
Splatoon
Super Mario 3D World
Mario Kart 8
Pikmin 3
The Wonderful 101
The Legend of Zelda: The Windwaker HD (A remaster, but worth at least mention)
Donkey Kong: Tropical Freeze
Hyrule Warriors
New Super Mario Bros
Captain Toad: Treasure Tracker
Kirby and the Rainbow Curse
As well as other 'lesser' games like Mario Party 10 and Nintendoland, and ZombiU which will soon lose it's exclusive status
And I'm looking forward to games like Yoshi's Wooly World, Xenoblade Chronicles X, Star Fox Zero, Fatal Frame, SMTXFE and Super Mario Maker. I imagine the new Zelda will the WiiU's swan song, but if that's so, I'll be alright with it.