There are some pure vocalists I love (Tony Bennett, George Michael), but then most "amazing vocalists" today typically end up on a different trac--like say, American Idol or Broadway.
I grew up listening to Otis Redding who, with all that rasp and holler, probably doesn't qualify as a great "singer," but that's a different thing than being a great vocalist, and Otis was truly great. Totally shaped my opinion of vocals in pop music.
Celine Dion is probably a better singer than M. Ward, but I know whose voice I prefer. It's an instrument like anything else... Tom Morello is a better guitarist than Britt Daniel, but Audioslave sucks.