Mike Patton truly is awesome, he has the most dynamic range I've ever heard, from straight-out crooner to some really freaky stuff, so he goes straight to number one.
I also think Thom York is amazing for high pitch stuff, and the same goes for Matt Bellamy, I'd say fifth and fourth respectively.
Trent Reznor is not only a good singer, but a talented instrumentalist as well, so I'd slot him in at Number three.
However, I think my choice for position 2 may cause a bit of controvesy, so hear me out:
I think Corey Taylor is an awesome singer.
I am well aware that on any internet forum, a statement like this can trigger an instant flame war between those who think Slipknot is crap because of the masks and refuse to even listen to their music and those who think Mic Thompson and the rest all lactate pure win, so I will do my best to spread the water of clarification onto the burning forest fire of the internet (btw, no one needs to remind me of the futility of this, we've all heard the clever metaphors).
First off, if you've ever tried to sing in a metal band (and failed like me!) you'll know know how hard it is to scream and sound cool, hence why most heavy bands these days either go melodic or go over the top and pretend they don't care that they sound like a cat being strangled at the bottom of a well. The fact that Taylor can scream well puts him a step ahead of most screamo. However, especially since the revival of his Stone Sour project, I think he's branched out a bit and expanded his range, leaving us with a singer who can scream and sing in the same song and sound good.
So, to sum up:
1. Mike Patton
2. Corey Taylor
3. Trent Reznor
4. Matt Bellamy
5. Thom York
Btw, this is my first post here, so I'm not sure what the standard of posting here is, but I've tried my best to keep within the rules I've found. If I've made any mistakes/said anything I shouldn't, please let me know.
P.S. Am I the only one who laments the relative sparseness of female vocal talent in metal. Please don't think I mean disrespect to the female vocalists out there, I just think it would be nice to see more of them.