If the only way someone knows a character came from a comic is when it says marvel before the movie it proves my point.
which means 100% of the people who saw Blade knows Marvel was the source of the movie. So yes they know it's comic.
If you change some facts from a comic back story the vast vast majority of viewers either won't know, or they won't care. They know what they see on the screen.
You want to change some shite up? Fine. As long as the end product is good.
You can't honestly say that Elba wouldnt be an awesome batman.
Changing the character's history or traits to a significant point? Yeah that is an issue with moviegoers. Look at IM3 and the shite it took because of Mandarin. Look at the shite MoS takes because of people's perception of the Superman (Donner/Byrne based). Frank Millers take on Batman is the essence of Nolan's trilogy-an accepted take on Batman.(jeph loeb as well)
If the end product betrays the core of the character, it doesn't matter if the film is good or not. When you adapt a comic to the big screen, the core must be intact. A black Batman takes away from that core.
I can honestly say Elba wouldn't be a good Batman, because Batman isn't black and being a WASP is crucial to the character. His family built Gotham City-a major US city for generations. They were the good people of Gotham. Bruce was on track to be entitled kid-was also thought to be an aloof playboy in some takes and a active CEO in others became a good a man as his forefathers who are all white,despite public perception of him.*
The moment you make him black, you take that core characteristic, and turn into the black struggle OR you paint it as a black Wayne family built the city of Gotham-is unbelievable,even for a movie in "heightened" reality. It simply doesn't mesh with the early beginnings of this country.
Black Americans didn't possess the wealth it required to make establish the Wayne empire-and that is ESSENTIAL to Batman.
*Which is my biggest gripe with Nolan's trilogy, he isn't Batman for his parents or until he finds happiness, he's Batman for Gotham. That flame is eternal.