MKD was decent and Halle's acting in the short clips that i've seen look ok although that costume is pure garbage. The race changes in my opinion have been minor ones. In some cases, I see how it wouldn't work. Malcolm X couldn't be a white guy for instance.
I see nobody mentioned the reverse. In the Spawn movie Priest was played by a white woman and the character is really a black man. Spawn's best friend was supposed to be black too but again he was replaced by a white guy.
OH NO!!! BATMAN IS A BLACK GUY!!!!!!!!!!!!!! LMAO!!!