There's an old joke about FFXI, in that there seemed to be more Sephiroth-clones in FFXI than there was in FFVII.

Luckily though that seems to be changing - although instead I see a lot of characters named either after celebrities or characters from Twilight/Game of Thrones/Harry Potter/<insert movie/tv show/novel flavour of the month here>.

It should also be noted that to do so is technically a violation of the Terms of Service, where it states your character name 'must not be taken from another intellectual property', but I don't think SE is particularly strict on enforcing that.