Japan is a money farm for certain genres.
Will Japan matter to the 360 (which seems to be your real question)? I'd say not really. If the 360 can get a strong consumer base without Japan and start turning a profit, they've already scored a major victory. Japan would be icing on the cake at that point.
For Nintendo, Japan matters a lot. If Nintendo can own Japan and Microsoft can lockin the U.S., Sony will get crushed in the middle. In which case, Microsoft wins... again.







