I’m not interested so much in the singers, but the performances. You can get a great performance out of a bad singer - Louie, Louie, for example. No one would identify Janice Joplin as a technically great singer, and some of her performances were train wrecks. But she had the ability to step it up a notch when it really counted, and put down some absolutely great vocal performances.
(henceforth calculates “some” as “three or four”)
I’ll also go with Bono in Sunday, Bloody Sunday.
Meatloaf has it all. A great voice, and I’m exhausted just watching his performance.
And I say again, Anneke van Giersbergen of The Gathering. Technically adept, emotionally invested, “Travel” (see earlier post) is her finest moment.
Well, it was a studio performance, but “Good Vibrations” shows how much control Brian Wilson had over his falsetto. It’s incredible how he hits high notes and fades without even a hint of losing pitch.
For live performances, I’d second Leon Russell if I had ever seen him live. I’ve heard that his singing live is at least as good live as his studio work.
Yes yes, and yes. The howling here is simply wonderful.
I’m not sure which song, or which part, but I think “At Budokan: The Complete Concert” album by Cheap Trick deserves somekind of attention. “I Need your Love”, “I Want you to Want Me”, and “Ain’t that a Shame” all sound completely awesome.
Obscure nominations, both from Living Colour: Cult of Personality and Type.
Corey Glover has an amazing voice.
Geoff Tate of Queensryche in Operation Mindcrime; it’s basically a rock opera. He demonstrates a pretty big vocal range, can really belt it out, sustains notes for a long time, shows good breath control in several long sequences. I’m not a vocal expert, but I think it was pretty impressive.
Robin Zander is one of the best.
My first thought was Joey Ramone on Bonzo Goes To Bitburg(My Brain is Hanging Upside Down)
I’ll have to toss in Cedric Bixler-Zavala’s performance in Cassandra Gemini with The Mars Volta. The man is ridiculously talented; definitely worth a listen.
Using this as our basis, Sam, I don’t think there’s any other choice than Bono’s performance of the song ‘Bad’ at LiveAid. That single song made that entire event and essentially moved U2 up from another up and comer who’d had some great songs to a supergroup.
And it’s not just the singing, God help me, it was that he was so clearly lost in himself and the event. Stumbling around the stage as if he were having a stroke and going into the audience to share some connection with them. It might well be the single greatest live song ever recorded.
While it’s possible the high notes you’re thinking of were Brian’s, it was Carl who sang lead on “Good Vibrations.” (Both Brian and Carl were capable of some great vocal performances.)
Springsteen’s “Glory Days”
Billy Joel “My Life”
It probably was. Didn’t hold it for very long though 
Freddie and the boys came out after U2 and put in the best performance I’ve ever seen. Freddie had that 80-90000 eating ouut of his hand. Nobody did big gigs like Queen. Everybody involved in the event says that Queen blew every out of the water on the day. Before the gig they were taken as old and tired. Not after.
Great performance by U2 though. They always put on a great show.
Some liveaid queen goodness.
We will rock you :- http://youtube.com/watch?v=E5d9fP6ASGo
Boh Rap and Radio Ga Ga, Ga Ga starts at 2:45 and is just stunning. You can see the waves of sound travelling through the audience. Remember this wasn’t a Queen crowd either. - http://youtube.com/watch?v=4FNoIDgNE6o
And if we’re going to have Aretha, we have to think about Patti LaBelle, too (Lady Marmalade, anyone?).
And don’t forget Tina Turner (River Deep Mountain High, Acid Queen, We Don’t Need Another Hero. I could go on).
I was barely alive for all of this, but having seen Live Aid on DVD and having been an avid fan of Queen for most of my life, I wish that I were present for just one performance. Freddie, even in his porno mustache days, was able to amaze and rile up a crowd like no one else I’ve seen.
Bob Seger, Night Moves. Now there’s a classic!
He put on quite a concert, too!!! 
Crosby, Stills & Nash.
Just awe-inspiring vocals there
Eric Burton and the Animals Sky Pilot