I prefer the sound of female vocalists, but Bob Dylan, Bruce Springsteen, Tom Waits, Van Morrison, Jackson Browne, Steve Earle, Townes Van Zant, John Prine, Ray LaMontagne, Jim Croce, Dave Alvin, Waylon Jennings, Kris Kristofferson, Willie Nelson, Johnny Cash, Richard Thompson, Boz Skaggs are a few male vocalists whose voices I like a lot. I used to like Elton John a lot, but I think it was more the lyrics than the voice. I am sure there are a lot more if I was to go back and look. Definitely Leonard Cohen. Eric Clapton.
I used to like Tom Petty a lot but that phase has kind of passed for me. Someone mentioned Nick Cave and from what I've heard of him I liked. Chris Smithers.