I just don't think the ES Lore has enough stand alone characters to make a movie or a TV series possible. In Game of Thrones you have a wealth of strong and interesting characters, almost too many for the TV series to do justice really. In the ES Lore pretty much YOU are the only real and dynamic character in the Lore.
That's irrelevant. They may not have been fleshed out in the lore- but that's the purpose of a television series - to flesh them out in a way they haven't been explored. Using your logic - every historical drama ever made involved wooden absolutely factual representations of every scarcely documented characters. You can draw personality from events.