As for RPG's, yes, most RPG's on the PS3 are JRPG's. Some are exclusive, like Demon's Souls.
However, the 360 also has it's fair amount of exclusive RPG's (I can tell, I have played and 100%'ed most RPG's on the 360) like Blue Dragon and Lost Odyssey *Drools at Lost Odyssey* and MagnaCarta 2
Ahem. Also, there is yer more Western type RPG's like Mass Effect ( Which came to the PS3 now though) and Dragon Age, but obviously, most are multiplatform. Also, upcoming RPG's like Elder Scrolls 5 and the lot are also multiplatform, and there are some many more RPG's on both like Eternal Sonata, NIER, Resonance of Fate, FFXIII FFXIII II, etc etc, so as far as RPG's go, both have a solid library.