If we want to be technical, we could just say that Caruso handily beats everyone named here. Now, whose voice do I probably relish the most upon first hearing? Probably David Bowie. If not him, Win Butler or Bob Dylan (who is a great singer by any standard I care about).
That guy from the Fray is pretty good, singing was never my strong point so I never had any idols... Also the guy from Alexisonfire on the album Watch Out!
Greatest vocalist ever? Wow...I think as far as raw power and soul goes, Annie Lennox is pretty high up, but I'm not sure about "best", there are so many out there! Cyndi Lauper has an incredible voice as well, and Tina Turner's voice is so raspy and gritty it digs into your soul.
i really really like Black Francis, but David Bowie and Tom Waits can stir me too. what can i say? if i love the music, i love the singer, range or technical skill not important ... what's most important to me is that the voice matches the music perfectly as an instrument ...
Past favorites of mine have included Layne Staley, Maynard James Keenan, and even Isaak Brock before he spelled bad news with Good News... I'm forgetting some I'm sure. I'm in a hurry.
If both of you are trying to persuade me that Lennon is a great singer, believe me I already know. My nickname is one of Lennon's songs for god's sakes.