CM Punk's reign as WWE Champion has been unusually long—unusual to the point that not an episode of Raw passes by when this longevity isn't mentioned. To put it into perspective, it's been longer than every individual World Heavyweight Championship reign, and the second-longest WWE title reign in 15 years.
This may beg the question: Where does CM Punk stand when it comes to naming the greatest WWE Champions of all time? Though his long reign stands out by recent standards, it's dwarfed by the multi-year reigns of Bruno Sammartino, Bob Backlund and Hulk Hogan.
A reign as long as that would be nearly impossible today, but that's due to the difference in how today's WWE works as compared to the then WWF/WWWF. Now, we have a weekly show and monthly title defences broadcast worldwide to a much bigger audiences, and changes in champions are necessary to keep things fresh and interesting.
So, it's clear there's more to being a great champion than just the length of a reign (though it certainly helps). Other criteria can include wrestling quality, how well-known outside of the industry's fans the wrestler is and how good their character and mic work are.
When it comes to wrestling quality, CM Punk is certainly one of the best. Bret Hart, Shawn Michaels, Kurt Angle, Brock Lesnar and Eddie Guerrero can compete in terms of individual in-ring skill, but when judging how good they are as champions, you have to look at the title defences.
Punk's title defences have been consistently great, with some especially fantastic matches with Chris Jericho, Daniel Bryan and John Cena.
This, of course, ties in with longevity; the longer someone's champion, the more good matches they can have. But even taken as an average, CM Punk's title defences have been relatively high quality.
How well-known a wrestler is beyond regular wrestling fans goes some way to explaining how big a draw they are. It's quite clear who rates most high judging by this criterion: Hulk Hogan, The Rock and John Cena.
It may be controversial to judge this way, as none of them can claim to be among the best champions in terms of in-ring skill, but they are the most recognisable to a wider audience. For CM Punk, it's early days. His time at the top is recent and ongoing, and it can only be judged in hindsight how successful a wrestler is by this measure.
Character and mic skills are the most subjective areas. Most wrestling fans love The Rock and Stone Cold Steve Austin in this way, whereas I personally don't.
Similarly, I thought CM Punk's time as a face, during his championship run was poor character-wise, certainly in comparison to his heel work which has been far more like the character of his infamous 2011 worked shoot that propelled him to the championship in the first place.
Ultimately, judging the greatest WWE Champion of all time is subjective, and it'll take some time after his reign ends before we can judge how CM Punk shapes up compared to his forerunners. But whether or not he's remembered as the greatest, from the string of great matches he's put on while he's had the belt, I'm confident his name will certainly be remembered among the greats.