definitely Freddie Mercury and Paul McCartney imo

I'd say Paul McCartney's voice was more pronounced in Wings than when he was in The Beatles. But he definitely has a powerful voice

For me it's Bruce Dickinson. His performances on "The Loneliness of the Long Distance Runner" and "The Evil that Men Do", among many other songs just gives me chills.

I think Mike Baker has a particularly powerful voice. I don't mean that it's loud and forceful, I mean that it's extremely effective at conveying emotion. Shadow Gallery simply isn't the same without him.

I'll think of others later.

Just check out JAMES LaBRIE!
http://www.youtube.com/watch?v=NRKtbHlM2Cg

James LaBrie was unbelievable, what with the crazy, unhinged screaming he was capable of (for proof of that, listen to the live EP Live at the Marquee), but he isn't that great now. His singing is still pretty solid nowadays though, so I won't say he sucks or anything.

LaBrie isn't really the best: http://www.youtube.com/watch?v=Y38tfrbFU7U

Dude, that was..... Bad. Just plain bad. Guess he wasn't at his peak there, uh?

Yeah, that was indeed terrible.

About LaBrie in general: he was pretty decent until 2002 I think. Now he has lost some of his usable range but it's his tone that...I don't know, sounds quite akward perhaps these days? He's definitely got downhill quite much I think.

Dunno about live, but his midrange on the newer albums is just fine.

I never found LaBrie to be that good of a singer, first time I heard him was on Metropolis Pt. 2, and I thought his voice was too "poppy" and nasal. The same thing goes for when I heard him on Images and Words. I like Dream Theater, and I don't think LaBrie is a bad singer, just has never been one of my favorites.

Maybe you'll like some of the early Dream Theater live material (from 1992 till 1994) James sang rawer and more aggressive live during those years. I didn't like LaBrie at all when I heard IaW for the first time but his live performences got me hooked.

http://www.youtube.com/watch?v=LWgdm096r_4
http://www.youtube.com/watch?v=S72RmOXiyRw (notice the difference between the studio F5# and in this one.)

This. His voice is just so... Prominent.

I'm going to cast my vote in for Christian Alvestam. His clean vocal range is remarkable. Truly astounding. His gutterals are, on the other hand, harsh, low and powerful barks. He is easily my favorite vocalist of all time.

Christian is definitely a great choice he is easily my favorite melo death/extreme metal vocalists and generally one of my favorite vocalists in any genre.

I never said I didn't like him, I just was never really amazed by him.

James LaBrie's voice has aged majestically. I love his tone on the last two Dream Theater albums.

Dio has already been mentioned, one of the most powerful voices of the 20th century

Nils Patrik Johansson, compared to Dio sometimes, not undeservingly so...

Rob Halford and Eric Adams used to be among the best vocalists in metal, but 'time is the only foe we have' and it's taken its toll...

also, not a big fan of Amon Amarth, but when Johan Hegg bellows 'don't spare anyone' - that's enough to instantly shit your pants...

and, I almost forgot, Kampfar's Dolk - very passionate and strong...

I have never not seen no double negative be used so unnecessarily not so. XD

Sorry, I couldn't resist, my just-had-to-be-a-dick-for-shits-and-giggles meter was overflowing.