Wow!
This question is kind of like choosing your favorite child. Seeing as how I'm an aspiring vocalist, I would kill to have the talents of so many singers. There are singers who have a really unique style, and there are those who are incredible live performers. If pressed against a wall with a gun to the head, I would have to say...........
1) Ronnie James Dio--The granddaddy of them all! He still has a powerful voice at the age of 64!
2) James Labrie--The voice that turned me onto progressive metal. I dare anybody to try singing like he does for three hours night after night.
3) Ray Alder--Though he's lost his high range over the years, he still sings with more power and emotion than most guys out there.
4) Daniel Gildenlow--If he can keep it up half as long as Dio has, this guy may very well reach the top of my list. This guy can sing ANYTHING!
5) Russell Allen--I get goosebumps listening to this guy. It's like listening to angel one minute and a caged animal the next.
Honorable mentions must go to Bruce Dickinson, Rob Halford, Mark Boals, Ian Gillen (why hasn't anyone mentioned him?), Harry Conklin, Khan, D.C. Cooper, Urban Breed (he's new on my list), and C.J. Snare (I don't care what anyone says. Firehouse rocks!)
Stay metal. Never rust.
Met-Al