Robert Downey Jr Was Set To Play Lex Luthor In "Flyby"

Director McG was in an interview discussing his new film, "This Means War" and during it he was questioned about his abandoned 2004 "Superman: Flyby" live-action film idea. He said that he cast current Superman, Henry Cavill as his "Man Of Steel". Now the next part was fucking strange, but at the same time, very fucking interesting, but McG mentioned that himself and Warner had Robert "Iron Man" Downey Jr signed on for the role of villain Lex Luthor in his film.
This is what he said about that casting and details on the film, "We had Robert Downey Jr. locked up to be Lex Luthor, which I think would have been extraordinary," McG enthused. But his pick for the Big Blue Boyscout is actually much less of a surprise. "Ironically, we liked Henry Cavill a lot, but we hadn’t cast him yet," he says of the actor currently wearing the tights in the upcoming "Man Of Steel." "J.J. wrote the script, and we got that to a really good place in the end," he says of the film, the first in a proposed trilogy. "But I’m to blame for [the film not happening]."
Could McG's Superman film have been great or even just worth watching or would it have been a train wreck, especially with the casting of Downey Jr as Luthor??? I guess we'll just never ever find out!!!