Here's an interesting graphic I stumbled across from something called Concert Hotels that graphs famous singers and their vocal range.
The Vocal Ranges of the Greatest Singers (via ConcertHotels.com; click on graphic for dynamic version that highlights songs on the low and high ends for each singer).
I'm not a singer so I can't speak to the accuracy of the list, although I'm shocked to learn Axl's range is so wide. But i do wonder where Geoff Tate, of Queensryche fame, might have landed. I've read of his seven-octave range, and this fan video below highlights that diversity.
What other dynamic vocalists do you wish were measured on the Concert Hotel list?