Animal Crossing is over 5m in Japan on DS, over 11m worldwide, essentially 3-4x the success of the GC version & Wii versions individually. One of the four DS games to top 5m in Japan
Friend Collection interest seems partially dependent on how many people are discovering and enjoying their Miis on Wii in any given week. I haven't actually tried to correlate them, but I think there is probably a decent R value there, maybe 0.6 to 0.8 - probably not super strong though as the game has to be in stock and DS hw impacts it too obviously. I don't see why it Tomodachi Collection can't get to 4.5m or so in Japan. Look at how it is trending against the DS mega hits in Japan. Animal Crossing DS may briefly fall behind the Tomodachi Collection pace over there.
People are difficult to govern because they have too much knowledge.
When there are more laws, there are more criminals.
- Lao Tzu
