Harry Potter's brilliant green eyes were yammered on about endlessly, too, but did it make any difference that Dan Radcliffe has blue eyes? Nope. Because eye color is not character.
This was actually down to the fact that whatever contact lenses the producers (or whoever) were using badly irritated his eyes. Bad enough it interfered with his health, his acting, or both. Can't remember. Hermione was supposed to have buck teeth as well, but the prosthetics they fitted her with were so cumbersome she couldn't speak.
And as far as the casting choice, let me put it this way; Jaime Foxx (sp?) played an excellent cowboy in Django Unchained. I loved his role in that movie, felt he was made for it.
But does that mean he should be cast to portray Clint Eastwood, John Wayne, or Donnie Yen?
Let's just say, not in my opinion. And that should more or less convey my opinion on You-Know-Who's casting as well.