Rock is so divided, but fortunately there are vocalists who transcend divisions
they are:
Axl Rose (unbelievable stage presence, insane vocals. sort've a mix between Joplin and Plant i guess)
James Hetfield (I like Megadeth more than Metallica, but he's got one of the best voices in metal... or used to)
Robert Plant (God)
What all three of these beasts have in common is that the music they sing to ROCKS. That's why it's called rock and roll, because it makes you want to rock and roll, to move. It energizes you.
Mike Patton's also damn good... Dio's good. Ozzy had a great voice years ago. I like Peter Steele's voice a lot. Mustaine had great, psychotic vocals on a few of those early Megadeth albums.
Paul McCartney's always sounded great