... -_-; Come on now, if you weren't satisfied with Mario Galaxy for a 3D mario game, what will satisfy ya?
My bitching aside, I think you've got it backwards. Nintendo's focus has always been top of the line 1st party, but good 3rd party games were a bit rare back in the days of the N64 (although, if ya ask me, the NES and SNES thrived off of epic 3rd party games, like final fantasy 1-6, while Nintendo still held their grip on their classic 1st party series). Since then, I'd say the 'Cube got a bit more great 3rd party support, and the Wii even more so. And I think that trend of increasing 3rd party support with the still kickass 1st party games will continue to flow on the Wii U. As you mentioned, AC is coming to the WiiU. Plenty of other series have been looking to jump on the bangwagon that is the Wii as well, but couldn't because of it's lower specs; things like Ninja Gaiden in all their graphical glory are finding their way to the WiiU as well. Two 360/PS3 series that I've loved for years, and have high hopes for.
And of course, we've got Skyward Sword, another SSB for both the 3DS and the Wii, etc. etc. Nintendo's flow of spectacular 1st party titles has always been superior to just "good", they're the best in that regard. Noone tops Nintendo's 1st party titles, IMO. I'm not saying such games are the best period, but in terms of their numbers and quality, Nintendo takes the cake here.
... Speaking of cake, I want a portal 3 on the WiiU... Think of the possibilities with the tablet's multitude of devices. But, that's a tangent.
So my opinion, is the WiiU will be full of win. If they capitalize on what they've promised regarding improvements over the Wii's shortcomings, (better wi-fi, namely; since they already announced scrapping FCs, they're clearly working on it), it could be even MORE of a success, I'd imagine. Both monetarily and in terms of a fantastic gaming experience.
Although, I'm curious how, or if they even intend to pull in the senior citizen crowd to their profit margin like with the Wii... Old timers aren't gonna have an easy time learnin' to use the tablet controller, unless maybe they've already had some notable experience with the Wii.