There's nothing more important for a new console than the launch window titles. it sets the tone of the console for the next year and gives players an idea of what kind of games people can look forward to. Nintendo flubbed this with the 3DS' poor launch line-up, but they've learned their lesson with the Wii U.
Nintendo wouldn't say what games would be coming on launch day for the Wii U beyond Nintendo Land and New Super Mario Bros. 2. They did, however, promise a total of 51 games would be out for the console by the end of March. That's a pretty large launch window, but it has plenty of great titles for the core and casual.
Here's some separate trailers for the more prominent launch window titles:
From here, the Wii U is looking to have a pretty solid launch window. It's now up to the early adopters to see if the Wii U will be an early success or fall flat on its face like the 3DS did at launch. It will be interesting to see if Nintendo has to pull another price cut this March like they did with the 3DS.