Wonder Woman's mythos presents many problems, but the basic hook to the character, particularly in her first appearance, is really not that hard. Diana's a newcomer, who has long dreamed of exploring the wider world, which she's been sent to save. She believes in peace, justice, all that stuff -- not really that different from other superheroes.
If a lesser known Thor can succeed as a movie with his epic fantasy background, so can a more well known Wonder Woman.
Hell, we already have a decent animated Wonder Woman movie. WB could use that as a kind of model for a live action WW film.