That's the sad part. Microsoft needs a top class RPG to get the Japanese Userbase. If I were then I'd thorw loads of money at SE for an exlcusive RPG.
The thing is, even if MS threw millions of dollars at Square Enix and secured Dragon Quest X for example, how many do you think are going to buy a Xbox 360 for just 1 game? Not many. The game would sell a few consoles, but no where near enough to justifying the millions it would require to make it happen. They need more then one title that appeal to Japan, Blue Dragon was a good start but MS needs to keep it up and eventually Japan will change their current negative view regarding the 360.
That is my take on it anyway. The same stands for the Sony and the PS3 right now. Just Final Fantasy XIII is not enough, that is why Sony are releasing more titles that appeal to Japan as well and together they can make a difference.