Batman arkham asylum is supposed to be Mark Hamill's last hurrah as the Joker. He won't do the voice any more at least that is he said he was retiring the voice.
Batman is voiced by the original actor from the animated series, the could not afford Bale and who cares really his voice was awful in the dark knight. Conroys voice might be a bit cheesy at times, but at least its not Adam West. Yeah sure some fanboys would have loved Micheal Keaton as the voice, but whatever.