One of the reasons I avoid fandom, or being called a fan is because fans tend to have this misguided sense of ownership. "I love it! It is mine! It should go in the direction I tell it to!" There are TONS of reasons why I avoid "fandom" anymore, and this is one of the principal irks among them.
I believe there are far better choices than Affleck, and I really don't agree with his casting as the Dark Knight, but I won't be opposed if he can actually pull off the role.
I do hope he does not try to go for the low growly voice that Bale had in the DK Trilogy. Much as I loved the DK Trilogy, that was one of the only things I think I found--annoying.
I honestly believe that Nathan Fillion (Firefly/Serenity, Castle) could pull off the role. He can be quirky and aloof, like Bruce Wayne, and he can play the tough guy role with equal gravitas.