i dont think audiences care if the hero is black white or brown per se.. just as long as the shyt is appealing in plot and direction. they watched a d list hero like blade with nearly as much interest and attendance as they did a media hyped up c/b-list hero like daredevil but with a much more positive response to the execution of Wesley's film that led to more sequels that each did well (all in all averaged in the 130-140ish million dollar range each). ultimately it was behind the scenes bullshyt in the 3rd film and not the audiences that killed that franchise. fukin terrible.
also, as we saw with ryan reynolds in green lantern.. aint nobody was tryna see that white boy save the world. But i bet if they redo that movie, fix up whatever was wrong with it plot, character, and direction wise (never saw it, never planned on seeing it, but i heard it was trash top to bottom) and repackaged it as a 'nolan' type film and vibe.. (more so just to further distance it from the more comic'y vibe that the first one had in the previews) then imo it wouldn't matter if they got the guy from jackie robinson to star in it as john stewart.. i feel that shyt would do numbers regardless.
so the bigger issue to me is more so the lack of black comic book companies (like what milestone was) along with the lack of black people in positions of power to politicize the featuring of the black heroes within the white comic book companies (i.e. dc and marvel)