CrazzyMan, you know that we estimate that by subtracting out Canada. I've already proven that Mexico and the rest of NA should favour Wii, making the real difference very small.
"OR it`s ok to SCALE American MONTHLY data, BUT NOT ok, to scale LTD???"
Not really, because the monthly numbers are fairly unprecise (5-10% off is possible), while the LTD is very accurate. This means that doing it LTD messes up the accuracy, while the monthly is already so inaccurate it doesn't make a lot of difference.
North America is not USA + Canada, in fact, they present less than 2/3 of the total population in North America.
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS