Top Ten Rock Vocalists

Ok slaw, here you go
Freddie Mercury, Robert Halford, Geoff Tate, Greg Lake, Robert Plant, Paul Rodgers, Glenn Hughes, Ronnie James Dio, Dennis DeYoung, Steve Walsh and Ann Wilson makes 11-oops😎
You are right nutty! About 10 being tough but I thought 25 might be too cumbersome for some.

czarivey, I disagree about progressive rock singers being poor by Nature! There are many great singers in prog rock.( I could go on and on) also it is not only vocal ability that makes a great singer butt the presentation and emotion they put into it

The following offered mainly in addition to the usual suspects already listed like Daltrey, Mercury, Page & Rodgers):
Gary Brooker
Jay Buchanan
Eric Burdon
Jack Bruce
Glenn Hughes (thanks to Nutty)
Janis Joplin
John Kay
Steve Marriott (+1 to Tooblue)
Chris Robinson 
Steven Tyler

A few missing names:
Jim Morrison
David Bowie (duh)
Stevie Nicks
Elton John (yes)
Tina Turner
Bono
Eric Clapton