For 3D Mario, I think Nintendo's focus is on performance, not super minimalist graphics for maximum clarity and performance (this has been the focus of Mario Kart). Galaxy 3, or whatever Nintendo is cooking, will probably perform similarly to Galaxy and at 720p. And it will, of course, make crazy good use of the hardware available for really big things.
I hate to say stuff that might come across as snide and condescending, but Nintendo-only gamers who don't buy other systems really wont know what hits them when it comes to the Wii U. It's a scary awesome new world for Nintendo's IPs and pretty exciting. If they deliver game engines and assets that make excellent use of the hardware, you're going to see Metroids, Marios, Zeldas and more looking like nothing you've seen before.
I'm curious to see how NSMB Mii ends up looking. As much as I hate the art direction, I don't expect it to look like last year's demo. That was using assets ripped straight from NSMB Wii. It would be tremendously disappointing if that's how the game looked, and it ran at 720p with no anti-aliasing :/.