Holy crap! How amazing is this? Well, I'll give you a hint.
The highest opening game on a single console ever, didn't make 50% AR even for a single week. It was at around 49.5%, but dropped after week 5. This is America only, its biggest territory, so a fair comparison to Wii Sports.
SSBB in America, Nintendo's biggest opening ever, is currently at 30% AR, and peaked at 33%, I doubt it will ever see that kind of sales again.
MKWii hasn't even broken 20% in Europe! It will in time though.
That's how amazing 50% is.
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS