Japanese tend to favor brands, they like Sony and Nintendo.
As been proven already, Microsoft is releasing those JRPG's and the Japanese are responding but with caution, because the original Xbox had a bad taste for them. The original Xbox was without JRPG's and very little software to appeal to them.
Now that the Xbox 360 has been released and Microsoft is now releasing the software that caters to them. They are now bitting, but its a slow process for Microsoft. I see the Xbox 360 hitting 700k or even 800k before this generation ends. This generation that we are in gives Microsoft some hope next generation as they build a fanbase.
I mean
Blue Dragon
Dead or Alive 4
Ace Combat 6
Dead Rising
Elder Scrolls IV: Oblivion
Eternal Sonata
Gears of War
The Idolmaster
Lost Planet: Extreme Condition
Dynasty Warriors 6 and many others....
They all cater to the Japanese hardcore audience, but it is a slow process. Its a wait and see and Microsoft will have a foot in the country of Japan. Its just going to take a couple of generations for it to happen.
But Microsoft needs to find the audience that is not hardcore and try to look beyond it. Even if MGS4 or FFXIII was manage to be released on the Xbox 360 in Japan. It wouldn't do any significant sales for the console. Since the Japanese will go with brand (Sony) and buy the version on that console. As we can see with Dynasty Warriors 6 in Japan. They like the PS3 version better...Its a wait and see type deal, like how we are seeing if the PS3 can keep its sales up.