http://forums.nutsie.com/viewtopic.php?t=18672
Tier 1: Breath support, register switching, register blending, pitch, vocal runs, consistency throughout registers, volume control, vibrato control, sustain, and diction.
Tier 2: Projection, Resonance, Endurance, Range, and Versatility(Tonal/Stylistic, Technical).
For criteria breakdowns, each criterion from either tier is worth equal points. Influence and impact have no bearing on a singer's placement.
The first 50 for now.
1. Jackie Wilson
2. Adam Lambert
3. Freddie Mercury (Queen, Solo)
4. Steve Perry (Journey, Solo)
5. Geoff Tate (Queensryche)
6. Steve Balsamo (Jesus Christ Superstar, Solo, The Storys)
7. Jeff Buckley
8. Tim Buckley
9. Michael Kiske (Helloween, Solo)
10. Chris Cornell (Soundgarden, Temple of the Dog, Solo, Audioslave)
11. Stevie Wonder
12. John Farnham (Little River Band, Solo)
13. Rob Halford (Judas Priest, Fight, Solo)
14. Roy Khan (Kamelot, Conception)
15. Mike Patton
16. Daniel Gildenlow
17. Brad Delp
18. Myles Kennedy
19. Jimmy Gnecco
20. Mark Boals
21. Todd Hall
22. Tobias Sammet
23. Matt Barlow
24. Bruce Dickinson
25. Ronnie James Dio
26. Roger Daltrey
27. Robert Plant
28. Roy Orbison
29. Al Green
30. Freddie Curci
31. Glenn Hughes
32. Lou Gramm
33. Russell Allen
34. Eric Adams
35. Dennis DeYoung
36. Axl Rose
37. Bobby Kimball
38. Arnel Pineda

39. Hansi Kursch
40. Ian Gillan
41. Cedric Bixler-Zavala
42. Jimi Jamison
43. James Labrie
44. Ted Neeley
45. Jon Bon Jovi
46. D.C. Cooper
47. Luther Vandross
48. Meat Loaf
49. Elvis Presley
50. Donny Hathaway
They are still updating the list but what say you?