Japanese developers came out early and tried to support both the XBOX and XBOX360. But on the whole, the majority of the games on the XBOX and XBOX360, as well as the advertising and lets face it, the target audience Microsoft was going for, was aimed at the 14-25 year old American Male gamer.
First Person Shooters, Sports games, Western RPGs, Action Brawlers.....none of this is a major draw for the Japanese gamer. Their major calling cards are games like Japanese RPGs, Tactical RTS, Anime based games, Adventure games, SHUMPS, Platformers, etc.
It was only with the development of the XBOX360, and Microsoft basically coaxing (IE subsidizing support) of many Japanese developers that any solid Japanese developers such as Namco, Konami, Mistwalker and SquareEnix even made games for the system. But even those games could barely break even their development costs, let alone generate interest in the Japanese market.
Long story short, a few Japanese developers making titles on a primarily American focused system won't get Japanese people interested. Not when they can have one of four heavily Japanese focused systems in their own country to choose from (five if you count PS2).
Six upcoming games you should look into:
