Actually the Japanese are not interrested by the 360 and its understandable. .
Look at the actual availiable line up of games for the 360. Nothing there for the taste of the Japaneses. No wonder why I never any Japanese servers on most of the FPS game I play.I see somes Asian servers on Counter Strike but not that many. For BF2 I see a lot of servers from differents countries but no Japanese servers at all.

Many Japanese games studios have somes games in progress, and when they will be availiable it should helps the 360 sales.But one thing is sure, like Ouchy said the Japanese are always supporting their own products first, and when the competitor is American, it definitly doesnt helps.