Who believes that Robert Plant

Dayglow...I concur. Marty was wonderful. I only say "was" because all I mentioned are dead (Byron) or no longer in their prime, including your pick, MB.

Correction...I guess Morrison is dead too.

He didn't R&R often, but for when he did George Gobel would be my top pick.

Kjweisner mentions Freddy Mercury, did the OP forget him, how can you? I love Plant and he is right up there among the most unique, at least in his heyday, but so far as Freddie is concerned, my guess is the OP forgot him or maybe Queen isn't to his taste? And by the way the question is presented, the question SEEMS to me about the most POWERFUL and original voice with great range, not just great voices, there are many. What are your thoughts Czarivey?

Are we talking about screamers? If not I think Muddy Waters has a pretty rockin voice. I can't say who is the best. A lot that has been mentioned are great. I am glad we have them all.