As part of their freshly-dropped quarterly financials, Nintendo have decided to lavish special attention upon two of its titles. While neglecting to provide us with individual sales data for all their first-party games, which they've sometimes done in the past, they would like us to know how many copies of Wii Fit and Mario Kart Wii they've sold. And the totals may surprise you! Because while Wii Fit's been a media darling, and has captured Nintendo a ton of good press with morning television crowd, it's sold "only" 3.42 million units worldwide since launch. That's a little over half of what Mario Kart Wii's managed, with the plastic-wheel-packing GameCube update managing to sell 6.42 million units worldwide.
It's clearly a matter of supply. You can't find either in strong supply anywhere. My girlfriend and I went to a Gamestop in an effort to buy Wii Fit, which they apparently still can't keep in stock. The guy was proud to say they finally had a handful of Mario Karts in, though, which she picked up for her nephew's birthday.
That all said, I'd be surprised at the immense success of Mario Kart if it weren't so damn fun. Honestly, I think I like it better than even Mario Kart 64. It's just a phenomenally fun game.