Best singers in rock....hmmm....
In no particular order:

Bobby Kimball (of TOTO) This guy wails in the studio and live....
Steve Perry (He will be missed in Journey)
Lou Gramm (I too have heard that his voice is not what it used to be but hey...having a near death experience will do that to a guy)
Brian Howe (Listen to any of the albums he did with Bad Company as proof)
Sammy Hagar (IMHO he kicks Dave's ass when it comes to vocal chops...I guess Dave puts on a better show)
Richard Page (Mr. Mister, 3rd Matinee...this guy was asked to replace lead singers in TOTO and Chicago....because he can sing his ass off!!)
David Coverdale (I don't even like Whitesnake a whole lot...but this guy is incredible)
Paul Rodgers (This is the guy that everyone tries to copy...and for good reason)

I could go on and on.....