The only one I've played is Nintendo Land, and it's not very fun after the first half hour.
Whoa wait what? Are you playing by yourself or something?
Nintendo Land is by far the most played game on my console and I consider it to be one of the best local multiplayer games I have ever played. It is fun as hell and we still play it maybe 3 or 4 times a week at my house. I would say it is the definitive Wii U experience at this point in time and would say it is the number 1 must have game on the system.
For perspective on my opinion I also have NSMBU, Batman, ZombiU, Lego City, some tank tank tank DLC, Trine 2, some virtual console games and have played COD BLOPS2.
NSMBU is really good too, you should know if you like 2D mario games and this is one of the best ones.
Lego City is great and probably cheapest.
Batman is cool but I have only put in a few hours.
ZombiU I like but I just haven't been able to get in to it too much, I just don't like First Person games that much.
Amazon is selling some games pretty cheap
Nintendoland for $28.74
I been thinking about Sonic Racing Transformed for $27.29....I heard it's good but I did not like the demo that much.
http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias=aps&field-keywords=wii+u