For the X360, there haven't been enough JRPGs of any various caliber to say if they've done well or not....There just isn't enough information.
Phantasy Star Universe did rather poorly. It sold around 100,000 units in the US + Japan (and maybe another 30-40k in Europe). However, PSU was a cheap crap port to the X360 that was no different than the PS2 version.
Enchanted Arms fared a little bit better on the X360. It did rather bad in Japan (around 22,000), but did quite well in the US and Europe. It sold around 120,000-150,000 copies in the US, and another 60,000-75,000 in Japan for a grand total of 204,000-250,000 units. I would say that the number wasn't too bad.
Outside of these 2 JRPGs, there really is no way to know. Blue Dragon isn't out yet. Having said this, WRPGs have fared magnificantly on the X360. Oblivion will sell well above 2m copies on the X360 (2m before a GOTY edition is insane). And M:UA sold around 750,000 copies on the X360.
Back from the dead, I'm afraid.
