To me, calling the first installment by the same name as the series as a whole is something that should always be avoided (I even call the original Legend of Zelda by its japanese name The Hyrule Fantasy). Given that we have been provided with an official title, I don’t see any reason not to use it. Not only is calling it Star Wars confusing (though admittedly only to non-fans), it’s awkward. You have Star Wars: The Phantom Menace, Star Wars: Attack of the Clones, Star Wars: Revenge of the Sith, and then just Star Wars? Or would you prefer Star Wars: Star Wars? Every entry in the saga has a subtitle. It seems counterintuitive for this one not to.