I grew up watching reruns of the Adam West Batman, thrived on Olan Soule playing the part during Superfriends, loved Batman 1989 with Michael Keaton (still the best live action Bruce Wayne and Batman for my money), and watched all of the other movies, TV shows and game adaptations.
With all of that in mind, my judgement is that Kevin Conroy is the voice of Batman. At least 2, maybe 3 generations of people have been raised listening to him give the best vocal performance of the character ever. I can't imagine anyone ever topping it.
It's sad to see him go, but the mark he left will never be erased. The voice role of Batman will never be the same.