I can't believe there are so many people that seem to think there is even a slight chance that Vita could sell anything even remotely close to what Wii U will do. It's really baffling because WiiU sure will have much much much more big system sellers than Vita among other huge advantages in comparison.
If I had to bet I would say:
Vita : 15-20 Mn
WiiU: 80 - 100 Mn
Really two totally different situations.
Will MK8 and SSB really make it sell 80-100 million? I doubt it would even reach 40. Just look at N64 and GC, even they had an MK and an SSB game.
Wii Sports is the game that Nintendo need to release on WiiU much more than SSB or even MK. I don't understand why people like you continue to compare the WiiU first party offering to the GC one while the Wii one is obviously a much better comparison and first party games on Wii were enough to sell 100 Mns console. This is absurd. Also GC when released wasn't in the same situation that WiiU is right now: WiiU has an advantage in terms of installed base not a huge disadvantage like the GC. People keep making comparisons with the GC or the N64 but that's a stupid one for that reason.
Nintendo still has by far the best selling first party ips, an advantage in terms of installed base, a console powerful enough to have at worse ports of most of third party games in the coming years... The only bad thing about WiiU sales are the actual ones but those can be easily explained by a lack of games that will soon be history, so really there is no reason at all to think this console won't sell really well in the next years.