The importance of the Japanese game market is extremely over rated.  In my mind Microsoft has been extremely successful in the United States lately, and thats what matters.  Microsoft is an american company, and Sony is a japanese one.  The difference is Sony has done very well in BOTH american and japanese markets, why? because Sony is able to create games that appeal to both American and Japanese markets.  Whereas microsoft focuses on the 18 year old American with games like Halo.  Don't get me wrong Halo is a great game, but there are very few other Microsoft first party titles that are as popular because microsoft thinks that there is no major market outside of that age-group.