Kevin Conroy possesses the kind of voice that could probably part the Red Sea. It's only fitting that his acting prowess from Batman: The Animated Series, Batman Beyond and five seasons of the Justice League series would bring the Caped Crusader to life in Arkham Asylum, and it's good to have him back. That deep, baritone pitch has been something that Christian Bale likely weeped at his inability to mimic, although it probably doesn't help that Conroy's normal civilian speech sounds like the voice of God with a touch of Clint Eastwood (also God).
On the other end of the spectrum, Mark Hamill, who is arguably more famous for voice acting than his lightsaber skills, is providing the voice of the Joker. It doesn't get much better than that. Unlike goofy incarnations of Batman's less threatening foes, Mark Hamill makes the Joker sound straight up psychotic. How psychotic? Expose some small children to Batman: The Animated Series, and it's 90 percent certain that they'll develop a sudden, volatile fear of clowns.