He's done so much more than that. While he is likely many animals you've heard, he's also Megatron and Soundwave from Transformers, Fred and Scooby-Doo, Apu from Aladdin (ok, this is another animal, but he got significant screentime), and Ralph the guard in Animaniacs.

He's Megatron, amount others.

Yeah, I think an argument can be made that frank welkers presence at the top indicates voice acting should be treated as an optional variant.