I would argue that "PC RPG"s and Console RPG's have grown up separately, and a lot of PC players scoff at the likes of Final Fantasy, because the Japanese aesthetic is so different, but in fact they can be as complex and mind numbingly boring as Baldurs Gate ever was (couldn't snore past the 3rd chapter myself

)
Every Tom Dick and Harry can write a PC RPG because it's an open platform. Quantity doesn't mean quality.
I won't argue whether it's "best" or not because that's highly subjective, but the 360 has a fantastic range of RPG's for all comers.
There's the "on PC's"
Oblivion, Two Worlds, Mass Effect,
Fallout 3,
Sacred 2 (Dragon Age is also coming to console)
And the (Console) exclusives:
Too Human, Eternal Sonata, Lost Odyssey, Blue Dragon, Infinite Undiscovery, Operation Darkness,
Tales of Vesperia,
Fable 2,
Last Remant,
final fantasy 13 and
Star ocean 4
While you could argue pure numbers I contend the 360 has the widest variety of RPG's instead of playing the same diablo rip-offs over and over again.
EDIT: the fact remains, as long as publishers make more on 360 than they do on PC, more and more developers are going to keep moving their products across.