Avatars in Hellenismos and Religio Romana

[Quintus Aurelius Orcus]

Salvete
On another list I'm on (Hellenic Pagan), someone started an interesting discussion on avatars in Greek and Roman polytheisme. For those who aren't familiar with the concept of Avatars, its from Hinduism and basicly is a diety that incarnates as a human being. Rama is an avatar of Vishnu, as is Krishna. These are seen in different ways by different people, and the way in which they are seen varies greatly depending on the context of the religion.
Soem might even suggest that Jesus was also a avatar of Jehova, but that is beside the point for this discussion. The author who asked that question has a point; there is some evidence to suggest the existence of avatars in both Hellenic and Roman polytheism, especially where the Gods come to Earth in human disguise to interact with humans.
Heroes are said to have been related directly to the Gods, as were Achilles, Herakles, Helen, the Dioskouri, Odysseus, etc. Can we look upon these heroes as avatars? Is Herakles an avatar of Zeus? Is Odysseus an avatar of Hermes, who in myth is his grandfather?
What of more exalted figures? Is Dionysos an avatar of Zeus, having been born to a mortal woman in myth? And what exactly is an avatar? Is the being the avatar is in human life essentially distinct from the deity that spawned it? What do you guys think? Are there avatars in Graeco and Roman religios or not?
valete

Quintus