So White Wolf's Exalted setting is actually a pretty good measure of the Chinese folklore religion?
Easily I give the links so even if you can't read it, you can still click the little speaker in the web page, and hear the sounds of it.
Well, I meant through a written medium, though that's an excellent work around.
Many polytheism hold this kind of concept, but most of them died out in history. Only some remaining the original aspects mostly folk religions. The basic reason is simple, because polytheism is likely evolved became many tribes conquered or combine with each others. So different gods if different in nature, and serve different functions in society will remain separately, too close they will become one but with many nicknames (most likely the more important function ones merged more).
However with those different in nature enough, but no longer serves functions anymore (lost demi-god), or those sub-characters of a nickname(alternative ego - abandon demi-god), or gods from the tribes which not fully merged yet, but slowly peacefully been assimilated, will not able to incorporated into the mainstream believes (free demi-god). They stay that way, till society decide their fate. Lost ones are most likely slowly been forgotten, abandon one to, but has the chance to re-integrated into others, free ones most likely gradually join the rank. It's for the greater harmony.
I think their function mostly been abandon, or integrated into angels, or becomes demons, in monotheism believes. And through time the importance of their roles changes as well, and finally the purpose of harmony no longer existed, and monotheism becomes a replacing old ones and aggressive religions. (Count how many times god strike down people in old bible), the origin of an angry god. And this idea is very dangerous as powerful, since if you can't continue your victory in conquering other people and strike down others, or been accepted by powerful conquerors, monotheism will not survived. Probably the reason why most major monotheism all have the same root. I believed many other monotheism believes are not that lucky. Abrahamic religions are really lucky, first dodge the conqueror from Egypt, if anything goes wrong in that journey, we may not have them today. And again dodged when Rome adopted it when its already a integrated empire and timing is right. And through the desert hardship another one rise, this time the conquer went well for a thousand more year or so, but stops when the force driving it lost in battle. And to their believers it will increase their faith as a separate group, since each time it seems like making the impossible, and the religious leader know about this, and make the most usages out of it. I believed that many are not that lucky, and when they died, there's no one left to tell the tell.
PS Another interesting aspect about Xian 仙, the demi-god, is that although the highest purpose is supposed to become one with the universe. Many people actually don't want to be deities, but to be Xian, the demi-god. You may wonder why, and reason is exactly because it has no obligation to serve the people, no responsibilities, with all the power. Sounds too perfect. Hence being real gods are hard, like working for your gods' bosses. But being demi-god, is like going on a vacation forever with all the expense been taking care of. And its a concept often related to another mortal concept - 俠 Xia. Someone do not belong to any governments, best with super charged abilities (not yet superhuman), and freely roaming the world as he/she wishes. Basically human version of Xian 仙. And more close to comic book superhero. People expected some form of responsibilities from 俠, but not because they have to, or force to, (there is no one controlling them), it's simply because he/she desires to take that burden willingly, and only ones willingly one can be called Xia 俠, but if he/she choose so, he/she can live freely away from people preventing the trouble, and doesn't affect the status as being Xia. Even less restrains on Xian 仙, they truly can almost do what ever they want, as long as it doesn't violate the balance of nature, and against the 'dao'