Those singers you enjoy,....that don't really have a great voice?

John Kay  ( Steppenwolf)  and Gary Brooker  ( Procul Harem )  Fantastic ....

Carole King

Leo Kottke. He described his singing as "Like geese farts on a muggy day."

Jorma Kaukonen.

John Prine.

Someone mentioned Leonard Cohen, but I think there was a big difference between his singing early in his career vs. later.

Somebody also mentioned Janis Joplin. Same thing - there was a tremendous difference in her voice between her early days (just a member of "Big Brother...") and when she was the headliner.

Roger Miller had a great voice to me because of the growl.  Listen to Engine, Engine #9, when he says these lines on later verses:

"I'm a little upset, yes"

"Coming down the railroad line..."

Roy Orbison was a superb singer that many couldn't match.

Great list folks!

Peter Green in last band he formed - Splinter Group

John Mayall