Male singers go:

1) Robert Plant and Freddie Mercury (RIP) (tied)
2) Roger Daltrey
3) Bruce Dickinson
4) Ronnie James Dio (may he RIP)
5) David Gilmour
6) Phil Collins
7) Don Henley
8 ) Dennis DeYoung
9) John Lennon (RIP)
10) Jon Anderson

Honorable mentions : Mark Knopfler, Lonesome Dave Peverett, Geddy Lee, Marvin Gaye, Al Green

Female singers:

1) Tina Turner (the Queen of Rock and Roll (not R&B as Beyonce proclaimed))
2) Christine McVie (shame she had to retire)
3) Linda Ronstadt (can't think of any other female singer who sang every genre thrown at her)
4) Ann Wilson
5) Chrissie Hynde
6) Stevie Nicks
7) Kate Bush
Sam Brown (UK female singer who can sing like no tomorrow and unknown to Americans (thankfully her work with David Gilmour and Pink Floyd exposed me to her))
9) Alicia Keys
10) Aretha Franklin

Honorable mentions : Annie Lennox, (though wasn't a fan but she did have a set of pipes) Whitney Houston (may she RIP)