Wow, a guy steps away from the forum for a few days, crap starts a'flyin, and now we're all trying to pick ONE QUINTESSENTIAL ROCK SINGER??? And with such weird strictures, that "Oh, he can't be considered, because he's bluesy", or "he's too R&B".
Bah. Why don't we try to figure out while we're at it who's the quintessential world leader? Or the quintessential religion of the world? Or better yet, how about who is the quintessential most attractive man or woman IN THE WHOLE WIDE WORLD EVER THROUGHOUT HISTORY?? (It's me, by the way...)
Get my point yet? Not to piss on anyone's cornflakes if you're really thinking that any sort of consensus could ever be reached, but this mick in Chicago thinks the premise of one quintessential rock singer is a little... out there.
That said, if you have to pick one, it would be Mick Jagger, bluesy or not. Jim Morrison is a bad Sinatra; listen to "Touch Me", and tell me I'm wrong. And sorry G5a, Natalie Merchant is about as "rock and roll" as Martha Stewart. Don't get me wrong; I actually own some 10,000 Maniacs CDs, agree with your points that the group wasn't the same without Natalie, think it was tragic that the first single that the reconstituted Maniacs came up with was a Roxy Music cover... but even though I'm sure Natalie's a nice person and all that, she sure as shit ain't a quintessential rock 'n roll singer.