According to Famitsu, Wii Sports was at 3,592,834 at the end of 2009 (it's been awhile since Wii Sports has been in the top 10, so it's harder to get more recent numbers). For that same period, they have Wii Fit at 3,555,555.
Not sure who ASCII Media Works are, but the 2 main video games sales trackers in Japan are Media Create and Famitsu.