not the song…
OK, if that’s true, then how about a list of great voices? My first:
Ronnie Drew, who sang with the Dubliners for years and years. If I could have any voice I wanted, it’d be something like his. 
Jon Anderson of Yes
Paul McCartney
John Lennon
Robin Zander
Jon Anderson
Joyce Kennedy (Mother’s Finest)
Gladys Knight
Cyndi Lauper (have y’all seen the Soundstage on PBS with her? I think it’s also on dvd…holy cow, what a voice!)
Wow - two Jon Anderson votes - well, there’s no mistaking his voice, that’s certain!
Mavis Staples
Tom Waits (really…listen to the early '70’s stuff…)
Gillian Welch
Rickey Lee Jones
Paul Rodgers
Robin Zander
Paul McCartney
John Lennon
Jon Anderson
Joyce Kennedy (Mother’s Finest)
Aretha Franklin
Freddie Mercury
(Yes…this is a slightly edited, and ordered into preference, version of Sean’s list…there’s a personal reason we have similar tastes.)
Why Freddie? Well, all I can say is that he might not be an obvious choice, and not my favorite singer, but if you EVER hear anyone else try to sing his stuff it becomes very obvious how good he was. Anyone remember the Freddie Mercury Tribute Concert. There was a long string of folks that couldn’t sing Queen songs at that thing and some were truly horrible. But there were a few that could. Ironically, George Michael and the guy from Extreme (don’t know his name) were two that could easily pull of Freddie songs…ummm…Liza Minnelli could not. (grin)
Yes, I thought George Michael did that pretty well, phoo!
these are all great lists - Mavis Staples, yeah!
Julie Covington.
If Lloyd Webber hadn’t been screwing Sarah Brightman, and Tim Rice hadn’t hadn’t been screwing Elaine Page, it would have been her as the voice of the West End musical.
Ali
Check out the acoustic Yes, These guys are getting on in the years but Jon’s voice still has it!
My current choices…
- J.R. Richards = He’s got almost 10 years of classical/operatic vocal training (~tenor) and is the singer/songwriter/piano/guitar player for the rock band Dishwalla (post-grunge, punk, electronic, alternative/prog rock genre). He’s also had 12 years of clarinet. They did a cool cover of “The Thrill Is Gone”, as well as some other covers (of Depeche Mode, Elvis, Led Zepp, etc.), altho most of their tunes are originals.
- Rob Thomas = Lead vocal for Matchbox Twenty. Country-ish alternative rock… at least country-ish to me. Great job on the old “Smooth” collab with Carlos Santana.
- Jon Anderson = Yeah, I will also include him for a lot of the Yes songs, but I couldn’t stand him for the compositions done back when he was collaborating in the Jon & Vangelis tunes.
Interesting one and difficult as depends what mood you’re in, however!
Paul Rodgers- Free/Bad Company
Rob Thomas- Matchbox twenty
Southside Johnny
Jeff Scott Soto
Bruce Dickinson-Iron Maiden
Bob Seger
Cyndi Lauper ( Amazing live)
Stevie Nicks
Celine Dion ( Don’t like all her songs but no doubting the voice)
Joanne Hogg-Iona
Robin Zander
Johnny Rzeznik
Bruce Dickinson
my vote goes for John Fogerty,of Creedence,never heard anyone cover any of them tunes,man that guy could belt it out,
Elvis Costello and his wife Diana Krall…how about that lead singer in the movie " the committments"
OK, next question - what about these people makes them stand out? 
Robin Zander - Range of ability and longevity. He can sing just about any style, and has for the most part with Cheap Trick through the years, and he makes them all emotional and convincing (including songs that have little meaningful lyrical content) — from pure punk screaming to soft slow ballads. His control is absolutely impeccable. He sounds the same live (seen CT many times) as in the studio and in some ways better. It’s easy to tell he doesn’t need any studio tricks to sound good. He also sounds just as good now as he did in 1977, and his voice hasn’t changed much at all except to get more powerful and more expressive. I expect some of his WAY high range isn’t there anymore, but he surprised me last time I saw them by hitting them (sounded effortless) just like he did long ago when CT pulled out some old songs they normal don’t play anymore. To me when it comes to pure ability there isn’t hardly anyone else in his class.
Phoo, Zander is one of those rare singers who has only gotten better over the years. Like you said, his control and expressiveness have increased noticably over time.
So…it’s cool to like Cheap Trick, right? In spite of some of those lyrically meaningless songs, right?
My philosophy is that r-n-r doesn’t need to have meaning as long as it’s fun. Meaning can sometimes get in the way. This is a great time to quote Eric Bennett (the bass player - not the doctor): “Play A and dance.” 
I’m gonna go with people I’ve seen live. It seems to be a consensus that is the true test of one’s voice.
Roger Daltrey (an undisputed vocal master)
Pete Townshend (aside from amazing guitar ability, he’s got a #### of a voice. Of course Daltrey has overshadowed this.)
Chris Cornell (the high notes he can hit will put a chill down your spine)
Tori Amos (very powerful and entrancing)
Chris Robinson (Okay, voice not as impressive live as on recordings, but his stage presence, the way he looks while singing a song, is second to none. He’s got you the entire show.)