The 3DS has remained the best selling system WW (I believe) since the price drop, and that's still with only a couple of popular games to its library. The fact that it dropped to 2nd place to the 360 in NA the last few weeks is perfectly normal (Gears 3 came out, after all). The holidays will paint a very nice picture for 3DS in both the east and west.
By the end of the year, 3DS will have an install base of over 10m WW.