I find the launch line-up of games to be very lacking, so I feel no reason to buy. I think that this is their greatest mistake and what will handicap the Wii U for quite some time. Wii had a great pack-in game with Wii Sports, and there was also Super Mario Galaxy which was innovative and very entertaining; Wii U just really has nothing that grabs you. 8-bit Super Mario Bros. retread? Seriously; that's the best they could come up with?
Super Mario Galaxy didn't come out until a year after the Wii came out. I'm not sure why you're complaining about New Super Mario Bros U, it looks like a great new Mario platformer and New Super Mario Bros Wii was one of the best 2D Mario games.
Also 2D Mario games are extremely popular, that's most likely the main reason NSMB U is a launch title for the Wii U. New Super Mario Bros for the DS sold almost 30 million copies and New Super Mario Bros Wii sold more then 26 million copies. Both casual and hardcore gamers love 2D Mario, so it makes sense to get it out as soon as possible for the Wii U.
It's also extremely unlikely Nintendo could of had a 3D Mario ready for the Wii U launch. EAD Tokyo were working on 3DS games like Super Mario Land 3D and OoT 3D last year. They wouldn't of had enough time to get a 3D Mario ready for launch.