I don't think D&D is the definitive fantasy, nor do I want it to be.
Unless you speak very broadly and equate D&D to the entire d20 movement, maybe. Within the broader scope of OGL/d20 you can find something that does nearly every type of fantasy I can imagine.
But D&D is more specific. As are each of the other iterations: Conan, Thieves' World, Midnight, Black Company, Cthulhu, etc.
What D&D does, however, is borrow from pretty much all fantasies and reinterpret their conventions, traditions and ideas in a native D&D environment.