Joey Ramone… nah jokes aside, maybe the singer from King Diamond… or Ronnie James Dio
I’d like to be there for that…just so I could make you both sing with me (a jazz singer with classical roots) afterwards. 
What, no love for Roy Orbison? When I opened the thread I thought he would be the first one mentioned.
That’s why Freddie Mercury belongs on this list. He did have a lot of range, but the power and the expressiveness of his voice are really amazing.
Along the same lines as Pat Benatar, I’ve always thought Ann Wilson (Heart) could have done opera given her range and power.
I find it interesting on all the Kristen Chenoweth comments.
She’s the OPPOSITE of this thread. She’s a trained opera singer who can sing in pretty much any style…not the other way around.
From her wikipedia article:
“Chenoweth attended Oklahoma City University, where she was a member of Gamma Phi Beta (Beta Omicron) sorority.[7][8] She earned a BFA degree in musical theatre[9] and a master’s degree in opera performance, studying under voice instructor Florence Birdwell.”
Well, that’s pretty much the way the music was written, isn’t it? That’s why it also worked well for Kristen Chenoweth.
As for Barbara Cook, just as with many popular sopranos, I find her voice a bit thin and unappealing, kind of squeezed or something, in the upper registers. Like Jeanette MacDonald. I like her otherwise, but not for opera.
Kathryn Grayson wasn’t too bad on that score, however. Good at least for light opera.
Roddy
+1 for ‘The Annies’ - Haslam & Lennox
How about k.d. lang? Her vocal chops seem to put her in that class, and she always sounds pitch-perfect.
Gee whiz - none of them even need Autotune.
I came in to say that not only could he have been an opera singer, Michael Bolton was never meant to be a pop singer and SHOULD have been an opera singer.
As few of my picks…
Sinead o’connor (if a suitably angsty opera could be found)
Peter Murphy of Bauhaus
Roy Harper
Brendan Perry of Dead Can Dance
Ronnie James Dio
Neat thread. Enjoying all of the comments. As has been pointed out, just because a singer may have the range does not mean that they have the talent. Screaming is not signing. A lot of the rock artists mentioned are atrocious live. I think posters are underestimating just how much work is done in the studio.
Did I miss it? Has no one mentioned Meat Loaf?
Are you…not familiar with opera? 
I did, in Post #12.
Well, there’s quite a few where people have the most amazing fights and tragedies while sounding like they’re having a wedding; that can be confusing if you’re not familiar with the lyrics. I recently identified (finally) a certain “warble” which I knew was from Mozart but not what - it’s the Queen of the Night, royally pissed off at her daughter; the lady is absolutely going for the Mother From Hell of the Century award, yet she sounds like a whole chorus of canaries (and could easily trigger one, that bit is the kind of thing that would have made my canary absolutely extatic).
I’m a huge a Meatloaf fan and have seen him live numerous times. He still struggles a bit live. A lot of rock stars have very limited range/talent that simply wouldn’t cut it outside of their genre. There are exceptions, like Elvis, but not that many.
Indeed, I was surprised that it took this long for Roy. Huge range (I’ve read that he could cover four octaves), but a beautiful, strong tone, as well.
Oh Bwoonhilda you are so wuuuuvvvvvweeee…
I’ve heard that Bjork works with a voice coach, so she might apply to this topic.
I’ve heard that smoking can ruin your singing voice if you’re a classical singer (obviously, there are many popular music singers who have smoked, and it hasn’t ruined their voices for their type of music, but I don’t know if they’d be able to make it as classical/opera singers if they smoke.)