Cannot comment on Rock or R&B because my listening pleasure resides with a different kind of music. However, my favorite male singers for different types of sound are:
For Musicianship: Mel Torme
For Range: John Gary
For Tonal quality: Vic Damone
For Style: Frank Sinatra
For Drama: Sammy Davis, Jr.
For The Show Stopper: Al Jolson
The best single theatrical tour-de-force performance I ever saw was Robert Merrill in "Fiddler on the Roof."