I guess I don't see how it is any different than BB. We already had seen in two movies that he became driven to become Batman when his parents were killed in front of him. The only thing they added was Ra's which is a totally different telling of the story.
BB got into a lot more detail about his origins, motivations, how he came by the equipment, etc. The first Burton film just barely flashed back to his parents being killed, and gave no idea even why he chose to dress up as a bat. Two movies later, BF got into that. Not exactly a comprehensive, beat-by-beat account of Batman's origin, as BB was, or as the Donner film was for Supes.
And if you think B89 was a sufficient account of Batman's origin, then why wouldn't you support a similar treatment for Superman? Just quickly throw the bare bones of his origin somewhere in a movie that has him already operating as Superman. Same difference.
Superman's origin story doesn't even need to be required as a main story plot in Begins...that is why I mentioned we could see snippets of it during flashback sequences at some crucial points during the movie. Perhaps Superman is battling Brainiac or Zod or Darkseid and he is remembering who he is and what he stands for, how he got to where he is now. That I took was the reason for the flashbacks in Batman Begins.
In that case, does it even have to be a "Begins", as in a story that takes place at the beginning of his career? Why not have him be an established Superman with a story that involves flashing back to relevant details of his origin? Or take the Golden Age/Byrne route, and have an established Superman who's just learning of his true origins? Best of both worlds--it's an origin movie, but he's established as Superman and the origin sequences don't take up the first half of the movie.