I'm the rare person who was never thrilled by the Galaxy franchise. For all its whimsy I always found it to be a mishmash of concepts from previous Marios that exhibits neither the strengths of purely-3D Marios like 64 or 2D Marios like World. It's linear like a 2D Mario but lacks the control tightness of an excellent 2D platformer and has a full range of motion like 3D Mario but doesn't allow for much exploration. The Galaxy series is still very entertaining, but it doesn't define what a Mario game should be for me.
NSMBWii looks like it might be more my speed, but I haven't played it yet. Shallow as this may sound, I don't like that it uses the standard, lifeless 3D renders of Mario characters that we've seen in promotional material for years. It makes the product look half-baked even though it may in reality be excellent. (Also, Nintendo games never drop in price =/)
Since this gen has seen an experimental Mario and a 2D Mario, it's time for Nintendo to revisit 3D Mario. I'll admit to bias as Mario 64 is far and away my favorite Mario game, but It's been 15 years since 64 and Nintendo has had more than enough time to revisit and improve on the formula. This much time without a "true successor" has been frustrating (although the new levels in Mario 64DS were great and were a tantalizing taste of what a potential Mario 64-2 could be) and Sunshine was a disappointment between its over-reliance on FLUDD, the Yoshi stages, and the overuse of tropical locales. With modern tech, a new 3D Mario would be astounding and is the most logical choice for Nintendo considering that the WiiU managed to slap some semblance of a traditional control scheme on the sides of its iPad controller. With Nintendo finally supporting true dual-analog (or...dual...slide-alog...or something), 3D Mario is best-equipped to take full advantage of this new control scheme.