NSMBU. Mario Kart 8 will do well enough, but NSMBU will likely have sold at least a million units by the time MK8 comes out. I can't imagine MK8 selling 5 times as much, especially with NSMBU being widely bundled.
When it comes to the original 10 million... MK8 is the most likely candidate. Just because it's Mario Kart on a console, one of video gaming's best combos for sales.







