The "casual" market that bought 30 million copies of NSMBWii is not going to care that this one is aesthetically identical. Conversely, the "hardcore" non-Nintendo fans won't care either way, because it's Mario; this won't be the IP to wrangle in new dedicated customers with dazzling HD visuals.
I cannot see anyone caring except for entrenched Nintendo fans, who will buy the console regardless just because.
Wii Fit plus LTD < Wii Fit LTD
Wii sports resort LTD < Wii sports LTD
Nintendogs and cats < nintendogs
Brain training 2 < brain training
Mario Galaxy 2 < mario galaxy
Move < kinect
The casual market might not care about graphical fidelity, definitely cares about novelty.
Sure the game will sell, but it will not outsell the original and will not drive console sales as effectively.