Analysis by Chris Harrington (indeedwrestling@gmail.com)

Certainly, this isn't the first time someone has attempted to rank UFC Fighters utilizing a ratings-approach commonly seen in Chess tournaments.

Since UFC fighters compete a lot less frequently than Chess players, I made some adjustments made to the formulas to produce more dramatic ratings differences.

The formulas used can be seen on the Wikipedia page for the "Elo rating system"

Notes

• K=300 (this has HUGE implications)
  
• Initial ranking for all fighters was 1000
  
• Draws/No Contest were awarded half points (0.5) to each competitor
• All other finishes (KO/TKO/Submission/DQ/Decision) awarded one point (1) to victor and zero points (0) to loser
• 179 UFC Events included (UFC 1 in Nov 1993 through UFC 132 in July 2011)
• 871 UFC Fighters ranked; 246 UFC Fighters have 5 or more fights
• No additional weight or consideration was given for different finishes (decisions vs KO) or title fights or rules variations or weight class implications or performance in MMA federations outside of UFC
  

Example

UFC 89 - Michael Bisping defeats Chris Leben via Decision (Unanimous)

• For example, if Bisping was rated 1485 going into this fight while Leben was rated 1277.
• The expected probability that Bisping wins was [ 10^(1485/400) ] / [10^(1485/400) + 10^(1277/400)] = 77%
• So, Bisping was expected to gain 0.77 points and he gained 1 point. 
  
• Leben was expected to gain 0.23 points and he gained 0 points.
• Bisping New Ranking Post-Fight = 1485 + 300*(1 - 0.77) = 1554
• Leben New Ranking Post-Fight = 1277 + 300*(0 - 0.23) = 1208

Results

Updated Top Current Rankings (as of 7/3/2011) - UFC & PRIDE results
1. Georges St. Pierre: 2153 rating after 18 UFC fights and 0 Pride fights; record 16-2-0 -- last match: 4/11
2. Fedor Emelianenko: 2108 rating after 0 UFC fights and 15 Pride fights; record 14-0-1 -- last match: 12/06 -- inactive
3. Anderson Silva: 2068 rating after 13 UFC fights and 5 Pride fights; record 16-2-0 -- last match: 2/11
4. Jon Jones: 1991 rating after 8 UFC fights and 0 Pride fights; record 7-1-0 -- last match: 3/11
5. Cain Velasquez: 1967 rating after 7 UFC fights and 0 Pride fights; record 7-0-0 -- last match: 10/10
6. Frankie Edgar: 1926 rating after 10 UFC fights and 0 Pride fights; record 8-1-1 -- last match: 1/11
7. Rashad Evans: 1919 rating after 12 UFC fights and 0 Pride fights; record 10-1-1 -- last match: 5/10
8. Gray Maynard: 1914 rating after 10 UFC fights and 0 Pride fights; record 8-0-2 -- last match: 1/11
9. Quinton Jackson: 1905 rating after 9 UFC fights and 17 Pride fights; record 19-7-0 -- last match: 5/11
10. Jon Fitch: 1848 rating after 15 UFC fights and 0 Pride fights; record 13-1-1 -- last match: 2/11
11. B.J. Penn: 1834 rating after 20 UFC fights and 0 Pride fights; record 12-6-2 -- last match: 2/11
12. Dan Henderson: 1806 rating after 7 UFC fights and 18 Pride fights; record 18-7-0 -- last match: 7/09
13. Lyoto Machida: 1769 rating after 11 UFC fights and 0 Pride fights; record 9-2-0 -- last match: 4/11
14. Junior dos Santos: 1761 rating after 7 UFC fights and 0 Pride fights; record 7-0-0 -- last match: 6/11
15. Carlos Condit: 1760 rating after 5 UFC fights and 0 Pride fights; record 4-1-0 -- last match: 7/11
16. Yushin Okami: 1748 rating after 12 UFC fights and 6 Pride fights; record 16-2-0 -- last match: 11/10
17. Forrest Griffin: 1744 rating after 13 UFC fights and 0 Pride fights; record 9-4-0 -- last match: 2/11
18. Dennis Siver: 1738 rating after 12 UFC fights and 0 Pride fights; record 8-4-0 -- last match: 7/11
19. Mauricio Rua: 1738 rating after 6 UFC fights and 13 Pride fights; record 15-4-0 -- last match: 3/11
20. Chael Sonnen: 1714 rating after 8 UFC fights and 0 Pride fights; record 4-4-0 -- last match: 8/10
21. Jim Miller: 1695 rating after 10 UFC fights and 0 Pride fights; record 9-1-0 -- last match: 3/11
22. Mark Munoz: 1694 rating after 8 UFC fights and 0 Pride fights; record 6-2-0 -- last match: 6/11
23. Andrei Arlovski: 1691 rating after 14 UFC fights and 0 Pride fights; record 10-4-0 -- last match: 3/08 -- inactive
24. Clay Guida: 1689 rating after 14 UFC fights and 0 Pride fights; record 9-5-0 -- last match: 6/11
25. Josh Koscheck: 1674 rating after 18 UFC fights and 0 Pride fights; record 13-5-0 -- last match: 12/10
26. Brock Lesnar: 1669 rating after 6 UFC fights and 0 Pride fights; record 4-2-0 -- last match: 10/10
27. Paulo Filho: 1658 rating after 0 UFC fights and 8 Pride fights; record 8-0-0 -- last match: 11/06 -- inactive
28. Melvin Guillard: 1611 rating after 14 UFC fights and 0 Pride fights; record 10-4-0 -- last match: 7/11
29. Sean Sherk: 1610 rating after 12 UFC fights and 1 Pride fights; record 9-4-0 -- last match: 9/10
30. Michael Bisping: 1604 rating after 14 UFC fights and 0 Pride fights; record 11-3-0 -- last match: 2/11

Updated Highest Career Rankings (as of 7/3/2011) - UFC & PRIDE results
1. Georges St. Pierre: 2153 rating on 4/11 (UFC 129)
2. Fedor Emelianenko: 2108 rating on 12/06 (Pride - Shockwave 2006)
3. Anderson Silva: 2068 rating on 2/11 (UFC 126)
4. Lyoto Machida: 2064 rating on 10/09 (UFC 104)
5. Mirko Filipovic: 2034 rating on 2/07 (UFC 67)
6. Jon Jones: 1991 rating on 3/11 (UFC 128)
7. Mauricio Rua: 1978 rating on 8/05 (Pride - Final Conflict 2005)
8. Cain Velasquez: 1967 rating on 10/10 (UFC 121)
9. Chuck Liddell: 1965 rating on 12/06 (UFC 66)
10. Frankie Edgar: 1959 rating on 8/10 (UFC 118)
11. Wanderlei Silva: 1957 rating on 10/04 (Pride 28)
12. Josh Barnett: 1949 rating on 9/06 (Pride - Final Conflict Absolute)
13. B.J. Penn: 1931 rating on 12/09 (UFC 107)
14. Antonio Rodrigo Nogueira: 1921 rating on 2/08 (UFC 81)
15. Rashad Evans: 1919 rating on 5/10 (UFC 114)
16. Gray Maynard: 1914 rating on 1/11 (UFC 125)
17. Quinton Jackson: 1905 rating on 5/11 (UFC 130)
18. Jon Fitch: 1885 rating on 8/10 (UFC 117)
19. Randy Couture: 1858 rating on 8/07 (UFC 74)
20. Brock Lesnar: 1827 rating on 7/10 (UFC 116)
21. Mark Coleman: 1823 rating on 2/97 (ufc 12)
22. Dan Severn: 1817 rating on 5/96 (ufc 9)
23. Thiago Alves: 1814 rating on 10/08 (UFC 90)
24. Dan Henderson: 1806 rating on 7/09 (UFC 100)
25. Dan Hardy: 1791 rating on 11/09 (UFC 105)
26. Takanori Gomi: 1784 rating on 12/05 (Pride - Shockwave 2005)
27. Chael Sonnen: 1784 rating on 2/10 (UFC 109)
28. Rick Story: 1780 rating on 5/11 (UFC 130)
29. Ricardo Arona: 1771 rating on 8/05 (Pride - Final Conflict 2005)
30. Rich Franklin: 1766 rating on 6/07 (UFC 72)

If you only include UFC fighters, and take any fighter than was new to UFC at baseline (1000), then these would be the results:

Highest Ranking UFC Fighters (5+ fights) - active & inactive (as of 7/3/2011)
1. Georges St. Pierre: 2140 rating after 18 UFC fights (16 wins, 2 losses) - last match: 4/11
2. Anderson Silva: 2035 rating after 13 UFC fights (13 wins) - last match: 2/11
3. Frankie Edgar: 1909 rating after 10 UFC fights (8 wins, 1 loss, 1 draw) - last match: 1/11
4. Gray Maynard: 1889 rating after 10 UFC fights (8 wins, 2 draws) - last match: 1/11
5. Cain Velasquez: 1858 rating after 7 UFC fights (7 wins) - last match: 10/10
6. Jon Fitch: 1839 rating after 15 UFC fights (13 wins, 1 loss, 1 draw) - last match: 2/11
7. Jon Jones: 1828 rating after 8 UFC fights (7 wins, 1 loss) - last match: 3/11
8. B.J. Penn: 1827 rating after 20 UFC fights (12 wins, 6 losses, 2 draws) - last match: 2/11
9. Quinton Jackson: 1784 rating after 9 UFC fights (7 wins, 2 losses) - last match: 5/11
10. Rashad Evans: 1782 rating after 12 UFC fights (10 wins, 1 loss, 1 draw) - last match: 5/10

11. Carlos Condit: 1749 rating after 5 UFC fights (4 wins, 1 loss) - last match: 7/11
12. Dennis Siver: 1736 rating after 12 UFC fights (8 wins, 4 losses) - last match: 7/11
13. Yushin Okami: 1728 rating after 12 UFC fights (10 wins, 2 losses) - last match: 11/10
14. Dan Henderson: 1707 rating after 7 UFC fights (5 wins, 2 losses) - last match: 7/09
15. Junior dos Santos: 1698 rating after 7 UFC fights (7 wins) - last match: 6/11
16. Jim Miller: 1698 rating after 10 UFC fights (9 wins, 1 loss) - last match: 3/11
17. Mark Munoz: 1685 rating after 8 UFC fights (6 wins, 2 losses) - last match: 6/11
18. Chael Sonnen: 1680 rating after 8 UFC fights (4 wins, 4 losses) - last match: 8/10
19. Josh Koscheck: 1629 rating after 18 UFC fights (13 wins, 5 losses) - last match: 12/10
20. Josh Barnett: 1622 rating after 5 UFC fights (4 wins, 1 loss) - last match: 3/02 - inactive in UFC

21. Melvin Guillard: 1611 rating after 14 UFC fights (10 wins, 4 losses) - last match: 7/11
22. Forrest Griffin: 1608 rating after 13 UFC fights (9 wins, 4 losses) - last match: 2/11
23. Sean Sherk: 1608 rating after 12 UFC fights (8 wins, 4 losses) - last match: 9/10
24. Clay Guida: 1599 rating after 14 UFC fights (9 wins, 5 losses) - last match: 6/11
25. Lyoto Machida: 1589 rating after 11 UFC fights (9 wins, 2 losses) - last match: 4/11
26. Frank Shamrock: 1580 rating after 5 UFC fights (5 wins) - last match: 9/99 - inactive in UFC
27. Brock Lesnar: 1574 rating after 6 UFC fights (4 wins, 2 losses) - last match: 10/10
28. Michael Bisping: 1566 rating after 14 UFC fights (11 wins, 3 losses) - last match: 2/11
29. Don Frye: 1556 rating after 10 UFC fights (9 wins, 1 loss) - last match: 12/96 - inactive in UFC
30. Kenny Florian: 1550 rating after 16 UFC fights (12 wins, 4 losses) - last match: 6/11

31. Mike Pyle: 1531 rating after 6 UFC fights (4 wins, 2 losses) - last match: 3/11
32. Frank Mir: 1524 rating after 18 UFC fights (13 wins, 5 losses) - last match: 5/11
33. Mauricio Rua: 1520 rating after 6 UFC fights (3 wins, 3 losses) - last match: 3/11
34. Andrei Arlovski: 1516 rating after 14 UFC fights (10 wins, 4 losses) - last match: 3/08 - inactive in UFC
35. Nate Marquardt: 1511 rating after 14 UFC fights (10 wins, 4 losses) - last match: 3/11
36. Diego Sanchez: 1509 rating after 16 UFC fights (12 wins, 4 losses) - last match: 3/11
37. Phil Davis: 1506 rating after 5 UFC fights (5 wins) - last match: 3/11
38. Matt Hughes: 1502 rating after 24 UFC fights (18 wins, 6 losses) - last match: 11/10
39. Jake Ellenberger: 1488 rating after 5 UFC fights (4 wins, 1 loss) - last match: 4/11
40. Gleison Tibau: 1484 rating after 14 UFC fights (9 wins, 5 losses) - last match: 5/11

41. Rafael dos Anjos: 1484 rating after 7 UFC fights (4 wins, 3 losses) - last match: 7/11
42. Rick Story: 1483 rating after 7 UFC fights (6 wins, 1 loss) - last match: 6/11
43. Rousimar Palhares: 1477 rating after 7 UFC fights (5 wins, 2 losses) - last match: 3/11
44. Matt Hamill: 1471 rating after 12 UFC fights (9 wins, 3 losses) - last match: 5/11
45. Anthony Johnson: 1471 rating after 9 UFC fights (6 wins, 3 losses) - last match: 3/11
46. Oleg Taktarov: 1469 rating after 9 UFC fights (6 wins, 2 losses, 1 draw) - last match: 12/95 - inactive in UFC
47. Thiago Alves: 1467 rating after 15 UFC fights (10 wins, 5 losses) - last match: 5/11
48. Vitor Belfort: 1463 rating after 13 UFC fights (8 wins, 5 losses) - last match: 2/11
49. Dong Hyun Kim: 1463 rating after 7 UFC fights (5 wins, 1 loss, 1 draw) - last match: 7/11
50. Alan Belcher: 1448 rating after 11 UFC fights (7 wins, 4 losses) - last match: 5/10

Fighters not included on this list with rankings higher than 1450 and less than 5 fights: Murilo Bustamante (1,519), Mike Russow (1,496) and Charlie Brenneman (1,472).

Highest Career Ranking of UFC Fighters (as of 7/3/2011)
1. Georges St. Pierre: max was 2140 after fight #18 (4/11) = defeated Jake Shields
2. Anderson Silva: max was 2035 after fight #13 (2/11) = defeated Vitor Belfort
3. Chuck Liddell: max was 1960 after fight #17 (12/06) = defeated Tito Ortiz
4. Frankie Edgar: max was 1957 after fight #9 (8/10) = defeated B.J. Penn
5. B.J. Penn: max was 1932 after fight #16 (12/09) = defeated Diego Sanchez
6. Lyoto Machida: max was 1908 after fight #8 (10/09) = defeated Mauricio Rua
7. Gray Maynard: max was 1889 after fight #10 (1/11) = drew Frankie Edgar
8. Jon Fitch: max was 1875 after fight #14 (8/10) = defeated Thiago Alves
9. Cain Velasquez: max was 1858 after fight #7 (10/10) = defeated Brock Lesnar
10. Randy Couture: max was 1857 after fight #7 (11/01) = defeated Pedro Rizzo

11. Jon Jones: max was 1828 after fight #8 (3/11) = defeated Mauricio Rua
12. Mark Coleman: max was 1823 after fight #6 (2/97) = defeated Dan Severn
13. Dan Severn: max was 1817 after fight #11 (5/96) = defeated Ken Shamrock
14. Thiago Alves: max was 1800 after fight #11 (10/08) = defeated Josh Koscheck
15. Rashad Evans: max was 1793 after fight #9 (12/08) = defeated Forrest Griffin
16. Quinton Jackson: max was 1784 after fight #9 (5/11) = defeated Matt Hamill
17. Rick Story: max was 1773 after fight #6 (5/11) = defeated Thiago Alves
18. Dan Hardy: max was 1771 after fight #4 (11/09) = defeated Mike Swick
19. Brock Lesnar: max was 1767 after fight #5 (7/10) = defeated Shane Carwin
20. Rich Franklin: max was 1767 after fight #7 (3/06) = defeated David Loiseau

21. Chael Sonnen: max was 1754 after fight #7 (2/10) = defeated Nate Marquardt
22. Matt Hughes: max was 1750 after fight #16 (9/06) = defeated B.J. Penn
23. Carlos Condit: max was 1749 after fight #5 (7/11) = defeated Dong Hyun Kim
24. Dennis Siver: max was 1736 after fight #12 (7/11) = defeated Matt Wiman
25. Tito Ortiz: max was 1730 after fight #11 (11/02) = defeated Ken Shamrock
26. Yushin Okami: max was 1728 after fight #12 (11/10) = defeated Nate Marquardt
27. Kenny Florian: max was 1723 after fight #11 (11/08) = defeated Joe Stevenson
28. George Sotiropoulos: max was 1721 after fight #7 (11/10) = defeated Joe Lauzon
29. Nate Marquardt: max was 1715 after fight #10 (8/09) = defeated Demian Maia
30. Dan Henderson: max was 1707 after fight #7 (7/09) = defeated Michael Bisping

31. Mike Swick: max was 1702 after fight #10 (6/09) = defeated Ben Saunders
32. Tim Sylvia: max was 1698 after fight #10 (11/06) = defeated Jeff Monson
33. Junior dos Santos: max was 1698 after fight #7 (6/11) = defeated Shane Carwin
34. Jim Miller: max was 1698 after fight #10 (3/11) = defeated Kamal Shalorus
35. Diego Sanchez: max was 1693 after fight #12 (6/09) = defeated Clay Guida
36. Mark Munoz: max was 1685 after fight #8 (6/11) = defeated Demian Maia
37. Royce Gracie: max was 1674 after fight #8 (9/94) = defeated Kimo Leopoldo
38. Oleg Taktarov: max was 1673 after fight #8 (12/95) = defeated Marco Ruas
39. Dong Hyun Kim: max was 1651 after fight #6 (1/11) = defeated Nate Diaz
40. Mauricio Rua: max was 1648 after fight #5 (5/10) = defeated Lyoto Machida

41. Josh Koscheck: max was 1648 after fight #17 (5/10) = defeated Paul Daley
42. Vitor Belfort: max was 1638 after fight #9 (1/04) = defeated Randy Couture
43. Josh Barnett: max was 1622 after fight #5 (3/02) = defeated Randy Couture
44. Sean Sherk: max was 1618 after fight #10 (10/08) = defeated Tyson Griffin
45. Ricco Rodriguez: max was 1613 after fight #5 (9/02) = defeated Randy Couture
46. Melvin Guillard: max was 1611 after fight #14 (7/11) = defeated Shane Roller
47. Forrest Griffin: max was 1608 after fight #13 (2/11) = defeated Rich Franklin
48. Shane Carwin: max was 1606 after fight #4 (3/10) = defeated Frank Mir
49. Andrei Arlovski: max was 1603 after fight #9 (10/05) = defeated Paul Buentello
50. Clay Guida: max was 1599 after fight #14 (6/11) = defeated Anthony Pettis

Google Spreadsheet with all Fighters