I think it's because the Japanese have a very different gaming culture to any other gaming nation with very few people actually being considered "hardcore".
Basically the Wii fits the Japanese audience perfectly. Apparently prime-time tv in Japan has taken a huge blow because too many families are playing their Wii's!
Last gen ps2 had alot of games for casuals and this gen the Wii has them.
The only time the PS3 and 360 will get a boost in Japan is when a game like Tales of Vesperia or Metal Gears Solid 4 is released.
(yeah i am putting the ps3 is the same boat as the 360)








