Evolution?

Scott,
In light of Triple H's comments that UFC is not evolving enough, I went back and looked at how many times the always cutting-edge WWE has had John Cena or Randy Orton main event a pay-per-view. I went back to 2005 when Cena was "drafted" to Raw. Here is the complete list. I believe I counted 51, assuming Cena-ADR main events Night of Champions. It's my rough guess that there have been 76 PPVs since June 2005, meaning the hip, fresh and always unpredictable WWE has had Cena or Orton in 2/3 of the main events.

In all fairness, some of them had Cena AND Orton. 

NoC 2011: John Cena vs. ADR*
SummerSlam 2011: CM Punk vs. John Cena
MITB 2011: John Cena vs. CM Punk
Capitol Punishment: John Cena vs. R-Truth
OTL 2011: John Cena vs. The Miz
Extreme Rules 2011: John Cena, The Miz, JoMo
WM 27: John Cena vs. The Miz
EC 2011: John Cena, CM Punk, JoMo, Sheamus, Randy Orton, R-Truth
TLC 2010: John Cena vs. Wade Barrett
SS 2010: Randy Orton vs. Wade Barrett (Cena as guest ref)
Bragging Rights: Randy Orton vs. Wade Barrett
NoC 2010: Randy Orton, Sheamus, Wade Barrett, John Cena, Edge, Chris Jericho
SummerSlam 2010: (Cena & Team WWE)
MITB: John Cena vs. Sheamus
F4W 2010: John Cena vs. Randy Orton, Sheamus, Edge
OTL 2010: John Cena vs. Batista
ER 2010: John Cena vs. Batista
SS 2009: John Cena vs. Triple H vs. HBK
BR 2009: John Cena vs. Randy Orton
The Bash: Randy Orton vs. Triple H
Backlash 2009: John Cena vs. Edge
WM 25: Randy Orton vs. Triple H
NWO 2009: John Cena, Chris Jericho, Mike Knox, Kane, Edge
RR 2009: Randy Orton vs. Triple H
SS 2008: John Cena vs. Chris Jericho
NoC 2008: John Cena vs. Triple H
Judgement Day 2008: Randy Orton vs. Triple H
Backlash 2008: John Cena, Randy Orton, Triple H, JBL
No Mercy 2007: Randy Orton vs. Triple H
SummerSlam 2007: John Cena vs. Randy Orton
GAB 2007: John Cena vs. Bobby Lashley
NoC 2007: John Cena, Randy Orton, Mick Foley, Bobby Lashley, King Booker
ONS 2007: John Cena vs. Great Khali
Judgement Day 2007: John Cena vs. Khali
Backlash 2007: John Cena, Randy Orton, Edge, HBK
WM 23: John Cena vs. HBK
NWO 2007: John Cena/HBK vs. Batista/Undertaker
NYR 2007: John Cena vs. Umaga
Armageddon 2006: John Cena/Batista vs. King Booker's Court
Cyber Sunday 2006: John Cena vs. King Booker
Unforgiven 2006: John Cena vs. Edge
SummerSlam 2006: John Cena vs. Edge
ONS 2006: John Cena vs. RVD
Backlash 2006: John Cena, Triple H, Edge
WM 22: John Cena vs. Triple H
NYR 2006: John Cena, Kurt Angle, Chris Masters, Carlito, HBK, Kane
Armageddon 2005: Randy Orton vs. Undertaker
SS 2005: Orton on Team Smackdown
Taboo Tuesday: John Cena vs. Kurt Angle vs. HBK
Unforgiven 2005: John Cena vs. Kurt Angle
Judgment Day 2005: John Cena vs. JBL