Good question. Michalczewski had the longer title reign while Chris John has a win over Juan Manuel Marquez that trumps any top victories from Michalczewski. People see Chris John's victory over Marquez as controversial but I recall the fight being very close that could have been scored a draw. Michalczewski probably rates higher due to his longer title defenses but him not facing RJJ does hurt him to some extent.
The win over Marquez and the series with Juarez is good enough to put John ahead. Too bad both guys spent most of their prime years feasting on crap.
Michaczewski. He was THE Champion of his division (unlike John), tied the record for most defenses in his class (he's no Foster, however), and looks to have fought better opposition overall. He also won a trinket in a division north, for whatever that's worth. John didn't fight many active top-10 guys, never became "the man" (nor did he try), and didn't venture northward.
I've got Chris John. DM was a long reigning cgamp but he didn't fight Jones or Tarver who were without question the best in that division. John fought and beat a prime Marquez within a couple of years Marquez beating Barrera, Pacquiao, Cassamyor, Diaz and Juarez.
I have an asterisk over the Marquez win though I felt Marquez clearly won it by a few points but I should go back and watch it sometime to do a proper scorecard. But my general feeling is that Marquez did enough to get the nod.
Quite close fight,but it thought John edged it with his distance management,he didn't let Marquez counterpunch enough.