NSMBU sold many consoles, in fact WiiU launch was quite successful. The problem wasn't NSMBU and NL but the lack of any other meaningful games for more than 6 months after that.
People were right also to say that games like Mario Sunshine, ZWW and others would be great assets for the GC the problem is that even before GC launched it was already a dead system because PS2 had already a huge installed base and even those games weren't enough to give it a chance to catch up. Thanks to its huge advantage in terms of installed base all third parties were going to support heavily the PS2 and didn't have strong incentives to even consider GC or Xbox. This time the WiiU doesn't have such a disadvantage and that's why the two situations can't be compared imo.