Your Top 5 Singers

Mike Akerfeldt (Opeth)
Steve Wilson (Porcupine Tree)
Mikael Stanne (Dark Tranquillity)
Maynard James Keenan (Tool)
Tori Amos
 
Daniel Gildenlow (Pain of Salvation)
Steve Wilson (Porcupine Tree)
Russell Allen (Symphony X)
James LaBrie (Dream Theater)
Doug Pinnick (King's X)
 
1: Marvin Gaye - Just don't take anything newer than 1981! I'm not too big a fan of his 60's work either, but his 70's work is cool! "What's going on" is a superb album and a song like "Mercy mercy me" showcases his fantastic voice! It's not like he has a 6 octave vocal range or stuff like that (his vocal actually sound a bit "choked" when he tries to hit the high notes), but the sound of his voice is amazing!
Isley Brothers - The same as with Marvin. Their "It's your thing" LP from '69 is pretty cool though! Ronald Isley has a really smooth and nice vocal!
Barry White - Always the man for some erotic music! I've heard a couple of songs of his from 1981 & 82 and they sucked!
Peter Steele from Type O Negative! Although his vocal also sound a bit choked when he tries to hit the high notes, I think his deep voice fits their music superbly! It also adds very well to the sombre and spooky mood in their music. As far as his vocal goes I still think "Bloody kisses" is the best album to showcase it!
Freddie Mercury's vocal on Queen's "Killer queen" is also really great! Gives me goosebumps! His vocal on "The show must go on" is also great and I must admit that it also is on "Radio ga ga", although I don't particularly like the song. If "Killer queen" was the only good vocal job he had done it would have been enough for me to mention him as a good singer, as it's so good!
Minnie Riperton - The best female singer EVER IMO!!! 6 octave vocal range!!! Enough said!
Suzi Jane Hokom - Truly a heavenly voice! You can hear that she progressed from her recordings with Lee Hazlewood in 1966/67 to the album she made with Virgil Warner in 1968. Her voice isn't that good on the stuff she did with Lee, but on "Lady bird" & "Summer wine" (which she also did with Lee) with Virgil Warner her voice is fantastic!
Patrice Rushen - Sometimes it sounds like she sings out of tune, but sometimes she strikes right to the bone! Some of her stuff is gross disco (and some are good disco), but some of her stuff is a bit more downbeat and calm. Stuff like "Where there is love", "Givin' it up is givin' up", "(She will) Take you down to love" & "Remind me".
I like Jeff Buckley's vocal too and I think it's better than his fathers, although I've grown tired of Jeff's music and I listen to Tim's music more than I listen to Jeff's, which isn't much though.
Sissel Kyrkjebø - The Norwegian singer. I have her first LP and it has two good songs on it. It includes my favorite composition of all time, "Summertime" (by Gershwin). This is clearly the best vocal-version I've heard of this fantastic track!!! I also saw some stuff by her on tv where she sang an operasong! GODDAMN, what a voice!
Axl Rose - Basically Axl sings like crap. If you listen to their live stuff where he sings over mellow stuff with that rusty voice you'll probably agree, but the range he has without going to falsetto is damn amazing! I would like to hear somebody who can duplicate for instance "Nightrain" after the solo!!! Impossible if you ask me!
I have to include Kari Rueslåten as well. I have 3rd and the Mortal's first LP, but I think the best work I've heard from her is the stuff on the Storm album. She would be in the bottom of my list though!

The rest I say would sing mediocre or okay.
Singers that I may not say that sing good, but I think is clearly in the better end of the mediocre/okay scale:
Tom Jones - I'm not a particular big fan of his music (although I have two records by him and he also sings the great theme for "Thunderball"), but I think he has a decent voice. It's gotten better than it was earlier in his career I think. Of course it should be as he should improve, but I think age might also have something to do with it.
Sting - I don't particularly care for his music either, but I also think he has a decent voice. I think his voice has improved much over the years. When I listen to some of the old Police stuff (like "Roxanne") he sings pretty crappy!
Aaliyah - I was a bit into some of her songs, but grew tired of it. Her voice on the verse of her song "More than a woman" is the closest you get in synthetic music to giving me the chills!
Heather Nova - I haven't heard much of her music and the stuff I've heard didn't particularly interest me, but her voice sounded pretty alright!
If I HAVE to pick someone in metal (which I'm not to keen on) I'd have to be:
Mikael Åkerfeldt - Decent voice, although I don't particularly like the growls (although they're probably the best I've heard).
Bruce Dickinson - Decent voice, nice range!
Mike Patton - I don't know what to say about him, but decent voice! Mr. Bungle is a piece of crap IMO though!
Glenn Danzig - Clearly among the best vocalists in hard(er) rock IMO!

Besides those four (and Axl) I don't think I've heard anyone in metal that I think sings good! Noone can convince me that a growling vocal sounds good. Some bands also try to mix in clean vocals, but often it just sounds crappy! An example of this is Dimmu Borgir's first album! Another example is Limbonic Art's first album, although it's clearly better than Dimmu Borgir's attempt! Emperor succeds a little bit with it on "Prometheus..."
 
In no specific order:

Mr. Tom Fucking Araya
James Hetfield
Ozzy Osbourne
Mikael Akerfeldt
David Vincent

I see a lot of us like a lot of the same people! My honorable mentions got to:
Jamey Shanahan (Hatebreed)
Zakk Wylde
Burton C. Bell
Dave Mustaine

And a big "FUCK YOU" to Bruce Dickinson!!!
I'm sure there's a thousand people who disagree with that, but too bad.
 
5. Ian Stuart (Skrewdriver/English Rose)
4. Chuck Schuldiner (Death)
3. Mikael Åkerfeldt (Opeth/Katatonia/Bloodbath)
2. Layne Staley (Alice In Chains/Mad Season)
1. Hansi Kürsh (Blind Guardian/Demons and Wizards)