I think the problem with fans is tolerance for stylistic variation. Although I'm not a die-hard comic book, I fan been a fan of other works, ie Harry Potter, were I let my perception of the books distort my judgement of the films. I've learned that things simply don't always translate between the mediums.
Micheal Keaton and Christain Bale had a "Batman" voice, and it makes perfect sense for the characters use of fear and his need to keep a secret identity. Of course this sort of thing would never show up in a comic book, which lacks audio, and an animated show for kids may want to keep the association between Bruce and Batman clear, as well as keep it family friendly. But in the case of the films, a voice change works to benefit this character of Batman as a funnel for his own emotional torment, turning Batman into a distinct entity of the Bruce Wayne persona.
And, on this note, I think Man of Steel took a stylistic approach to differentiate itself from 1975 version and it worked to the film's benefit. What's great about the film is you do get the impression that Superman is a hopeful believer in people and an idealist, but by challenging him with the question of which people, Kryptonian or humanities, he is forced to make a very black and white choice, while confronting his own demons and his own identity. In the end, I felt that it was a Superman film, not because he blindly fought for humanity, BUT because he was bounded to both Earth and Krypton and willing to defend them, and when something like Zod comes around, he is willing choose the greater good over his wants and needs.
Man of Steel was an average film, but it's style was solid and I think if done right Superman and Batman could be a fantastic film within the series.
EDIT: Ben Affleck? Yes! He's a better director, but probably the only A-list choice that would stand out on screen. His film's, specifically The Town, also tend to be stylistically within the same range as Nolan.