Better ask: Why is't doing insane in japan..:)
In the vest it's pretty good to.. and i remember back when it hit 4 mill. faster than ds in the us..
Soon the 3DS XL.. And this holiday, will make it even bigger.. true cult.. and i bet that wii u and 3ds will be in top in every region.. After holiday it will stay that way.. just wait and see :)
Actually.. In some holiday weeks.. It's very likely, that we will have 4 nintendo consols in the top :)