I always assumed that Japan had a healthier adult collector base. One of the things I could always count on in Japan - If you make it big there, Japan will never let it die!! Maybe that's not so true any more?
You need a healthy child collector base for a toyline to thrive though. The majority of toy consumers are always going to be children. There are entire schools in Japan that are closing down because of their declining birthrate. People in Japan need to make more babies!