As someone who’s currently playing Mario Galaxy 1, I can attest to the fact that the game has sporatic, yet severe issues. Roughly 15-20% of the time I’m playing the game, I’m swearing a blue streak at the [censored] [beep]ing god-damned piece of [beep] camera. Getting killed cause you can’t see what’s going on flat out sucks. It manages to be worse than Mario 64 in this regard because of the unusual geometry in the levels. Another 5-10% of the time I’m having a problem with the controller deciding to correlate the direction I’m pushing the analog stick, and the direction Mario moves, in rather odd ways.
Of course, we ARE talking about Super Mario Galaxy 2 here. I mean, this is a Mario game from Nintendo, and last I checked, New Super Mario Bros was to this day regularly showing up on monthly top sales charts - nowhere near the top, of course, but if it’s a relatively slow month - there is is, ranked #16, moving another however many units. And this is five years later. (Edit: I just checked - between April 1 and Dec 31 of last year, it sold 3.7M copies.) So if MG2 hasn’t sold ten mil yet, well, I’d venture all Nintendo has to do is wait.
And if they for some reason get really desperate, they can always wait a while, then release Super Mario Galaxy Collection and include both games in one package.
Edit: And apparently New Super Mario Bros. Wii has sold 21.2M total copies, 6.58 million of which between April 1 and Dec 31 of last year. Super Mario Galaxy 2 “only” sold 6.15 million during that same period. (It wasn’t out before Mar 2010 anyway).
So Galaxy 2 got beat by a pretty significant margin by a game that was released six months earlier. Of course, there was maybe six to eight weeks in that reporting period where NSMB Wii was on sale, but Galaxy 2 wasn’t out yet. Too bad Galaxy 1 isn’t in either source document so we can’t see how it did.
My sources:
http://www.nintendo.co.jp/ir/pdf/2011/110128e.pdf
http://www.nintendo.co.jp/ir/pdf/2010/100507e.pdf