Blue Dragon *belongs* to Microsoft, being published by Microsoft Game Studious themselves. (Unlike Enchanted Arm, which did have the 'Only On Xbox' sticker but was published by Ubisoft.) It's highly unlikely it'll be going anywhere else. Blue Dragon was/is a key part of Microsoft's effort to penetrate Japan and they pumped money into Mistwalker for their development.
Mistwalker isn't owned by Microsoft, but Microsoft 'owns' both of the 360 games that are coming out from them. They aren't going anywhere.
It's true that people who are most familiar with the names behind the game already own PS2s and such, and that's exactly what they were aiming for. It was a combination that, based on legacy, couldn't fail in Japan. And it didn't fail. It didn't do super good when compared to other franchises, but it's been the best-selling 360 game by quite a margin. In its launch week, it sold over 80,000 copies which is relatively excellent--especially considering it launched against a freakin' Gundam game (which I own, and is awesome).
So while it wasn't exactly a blockbuster in Japan, it was definitely a hit for the 360.
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As for the other games, I'm playing Persona 3 now and don't feel the need to play any other console JRPG for the rest of the year. It's fresh.
I will buy Blue Dragon. I wasn't a fan of the .hack series. I never touched Wild Arms before, but I might get V just because of this. Eternal Sonata is pretty, but the gameplay didn't really click for me. I'll probably buy it next year after I recover from the banruptcy that will happen after this 'holiday' season. Lost Odyssey looks fairly graphically impressive, but the gameplay doesn't look like anything special either.
While I may not be looking forward so much to Blue Dragon, Lost Odyssey or Eternal Sonata, I do want more Japanese-styled games on the system. So, my way of telling the companies I want more of them is to buy the games. If I can afford it.
But yeah, Persona 3. Full stop. My JRPG of the year.