It's a bit complicated, but I'll do my best.
When Jack created the New Gods, it's pretty clear from the art that his idea for the Old Gods were the Asgardians. Specifically, the Marvel Asgardians. At the time, there were no classical gods regularly appearing in any DC books, so there wasn't any confusion.
After Crisis, George Perez brought the Greek Gods (and later, the Roman gods) into prominence in his WW run, and DC also brought Captain Marvel back into the public eye. So it was suggested (in Perez's "History of the DC Universe") that the Old Gods were actually the Titans of Myth, and the great war that created the New Gods was their battle with the Olympians.
That didn't last very long, and was soon forgotten. The Old Gods became disconnected from any terrestrial mythology, although they tended to have faux-Norse names. When a few Norse gods started showing up, the similarities were chalked up to a weird connection between the world of the Old Gods and Asgard.
That's more or less how things sit now. |