Are you serously making this very dumb comparison? Seriously? NSMBU is not even a remake. It's a port of a game that reuses assets from previous NSMB games. NSMBU looks like a Wii game. NSMBU never was a true new 2d Mario adventure.
Beg to differ on that.
And while a new 2D Mario should outdo NSMBUD, I don't think it will beat SMM2. In case you didn't notice, many are taking SMM2 as their 2D Mario already.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454