Microsoft has proven that they can make headway by at least trying (which is something they didn't do with the original Xbox at all, practically), the main problem is that the 360 really had nowhere to go in the Japanese market. Lack of focus on Japan in the earliest periods of the 360 meant that they voided the big momentum advantage they had over PS3 in other regions, momentum advantages that they coupled with their strong online network to solidify that momentum advantage
As far as the Japanese third-party market goes, Microsoft gets squeezed out, except for titles that Japanese 3rd party made for stronger appeal in the West, and even then, multiplats do nothing to give you an advantage (at least as far as Japan itself goes). As far as 3rd parties looking for exclusivity goes, it's the same problem that the Wii faces from Western developers: either just go for the established "hardcore" userbase (PS3), or go for any number of the lower-cost platforms (Wii, PSP, and DS) all of whom are viewed as viable platforms for full-scale games in Japan (whereas Western developers disdain proper development for all three platforms), so there's really no reason to make an exclusive, and a multiplat will just end up being more Sony fodder
Moneyhatting exclusives and forming partnerships (a la their former partnership with Mistwalker) got them much further with the 360 than the Xbox, but it was their failure to do so right at the beginning, and then broader market dynamics that they have less control over, that have marginalized their Japanese position utterly
Monster Hunter: pissing me off since 2010.
