I see what some deem as rock others would classify as "easy listening".
I would say my vote(s) go for Freddie Mercury because of his range, Maynard James Keenan from Tool for range/uniqueness, and Brandon Boyd from Incubus, just great all around talent (vocally).
I see Mr. Babcock is sticking to his "heavy" roots with his vote for Halford from Judas Priest.