Your thoughts about Ben Aflac being the new Batman in Batman vs. Superman?
Personally, I think the writing is more essential than the actor.
People have an inherent idea/bias/prejudice of a persons personality just by looking at them. Hence the desire for pictures on online dating sites.
If they write a story completely out of character for what someone looks like, choose an actor completely at odds with the story, or make the story so bland and vague it can really be played by anyone with little effort, then it's going to fail and most of the time blamed on the actors.
I don't think Ben Affleck will have any problems being the new batman if the story wasn't written for someone else, or they don't try to make him a character meant for everyone.
If he was just shoe horned into a story because of some kind of contract or star power, then it's going to fail.