Though the presentation in Galaxy is better, I do think both games deserve just about a perfect 10 for being nothing but pure entertainment. But that's just me.
As for Japan goes, I'll say it again, they seem to accept the 2D Mario titles way over the 3D ones. And the fact that this game can be considered a party game? You know they are going to eat it up!
There is a similar trend with Zelda to isn't there? Haven't the handheld games been performing better than the console games?
I think if games like Galaxy(Zelda to) or future 3D Mario's want sales numbers like NSMB/W they are going to need multiplayer.
And not phony extra Wii pointer multiplayer or phony Tingle GBA multiplayer either, but real deal NSMBW multiaplayer.
It is very obvious with Galaxy, Wind Waker, NSMBW, and 4 Swords, that Nintendo is trying to make multiplayer in the core titles of these franchises. Remember the interviews about Miyamoto trying to have Mario and Luigi running around in the same 3D space but it just wasn't working? Well you can bet that those ideas must come up often and now they are seriously trying to get those things running. I mean the co-op element of NSMBW adds such an amazing new element to Mario, I do not want to see another 2D Mario without it.
And these co-op platformers will sell way more than the single player ones that's for sure. Applying the same ideas from 2D to 3D could work for Mario I'm sure, how multiplayer could work in Zelda where the other person actually feels important seems very difficult but it is gonna happen sooner or later. After the draw of motion controls for the next console, I just know full on multiplayer maybe 2 players for an entire Mario or Zelda Adventure will be the latest draw.