The 3DS needs software just as badly as Vita does. For the 2nd year straight, Nintendo is relying on a Mario to keep sales above 'subpar', while bringing nothing else of value over from Japan or by releasing timed-exclusive games for the West. Nintendo of America has been absolutely terrible for going on 3 years. To be honest, even if Japan's major hits would not sell more than 250k here, that is still ~250k Nintendo is not making profit from.
I personally haven't purchased a 3DS and do not plan on it because of this. Their strategy just screams tired.
The best-selling 3DS game in the West released this year is Kid Icarus: Uprising. Not a Mario game. Not a timed exclusive. Next in America is Resident Evil, a 3rd-party title. Soon, Kingdom Hearts 3D will join those two.
So far this year, Nintendo has released only a single Mario game in the West, and it hasn't sold very well. What's keeping the 3DS "above subpar" is mostly strong third-party support. The console would continue selling "above subpar" for the rest of the year without Mario games; instead, it will sell like hotcakes.
As of NoA, I am aware of only one first-party 3DS game that isn't being localized this year: Fire Emblem. It's coming next year, so hold your horses. NoA doesn't decide what games get localized, anyway; NoJ does.