After looking at the alphabet soup, we finally come to the lineal championship and the Ring Magazine championship - the two ways someone can truly claim to be the world champ in boxing. Both championships have the same foundation - the man who beat the man is the man, period. If there is no 'man', then a new one is created when the best beats the best.
While the Ring Magazine titlist isn't necessarily the true champion, a lot of people use is as a proxy for being the true champ. The rules for becoming the champ are rather simple: If you beat the champ, you become the champ, and if there is no champ and If the guy ranked #1 and the guy ranked #2 fight each other, then the winner is the new champ. Occasionally, there are exceptions to this rule, leading to the divergence between the Ring champ and the lineal champ. If agreed by the editorial board of the magazine, then a fight between #1 and #3 can create a new championship. This is usually reserved for special circumstances, such as if #1 already recently beat #2, or if there's a good reason why #1 and #2 will never fight (such as the Klitschko brothers). Also, when Ring ceased publication for a while, it did not pick back up its old champions when it restarted publication, which led to some divergence in the Light Heavyweight and Flyweight divisions.
So the champ comes down to the rankings themselves. Contrary to somewhat popular belief, Golden Boy, owner of the Magazine, does not control the rankings, and Oscar de la Hoya does not manipulate the rankings for his own benefit. Instead, the rankings are compiled by the magazine's four man editorial board, with significant input from 37 panelists who submit their own rankings. The panelists include a number of prominent boxing writers and commentators, such as Joe Tessitore, Barry McGuigan, Nick Charles and Doug Fischer, While this isn't a perfect system, it does tend to get a more balanced viewpoint than rankings compiled by only a few people, as they are compiled by most of the ABCs. The biggest knocks are that the panel does tend to be very Anglocentric, with all but a few panelists hailing from the United States or England, and that the editorial board still has room to move guys up or down in its discretion.
What actually constitutes the lineal championship is a source of constant debate. When there was one sanctioning body, it was easy - the champ of that body was THE champ. Even when there were two bodies, for the most part, when one person held both belts, he became the champ. With four major belts run by money grubbing organizations who like to strip titlists in order to maximize revvenue, the equation becomes much more complicated. If you needed to get all four belts to become lineal champ, then the only lineal champ of the four belt era would be Bernard Hopkins at middleweight (and his successors). The two more reasonable approaches are that someone becomes lineal champ when #1 beats #2, or when someone is the only person in a weight class who can legitimately claim to be the top dog. For the purposes of this article, I'm taking the first approach, allthough because there is a split view on this issue, and because there is no specific set of rankings that every individual relies on, calling someone the lineal champ is inherently subjective.
While there are no less than 90 fighters who can claim to be an ABC titlist at the moment (whether as a regular champ, super champ, interim champ, silver champ or double rainbow across the entire sky champ), there are only a few people who can claim to be the true champion of the world right now:
Heavyweight - Wladimir Klitschko became the Ring champion when he beat Ruslan Chagaev, who was ranked #3 at the time. The lineal championship is vacant, as Wladimir will never fight the man at #2, his brother Vitali.
Light Heavyweight - Here's an area of some controversy. Jean Pascal was recently named the Ring titlist, and after they restarted publication, Roy Jones became their champ on a 1 vs. 3 exception. But you could argue that either Pascal or Zsolt Erdei is the true lineal champion at the moment. Erdei's lineage traces from beating Julio Cesar Gonzalez, who beat Dariusz Michalczewski, who beat Virgil Hill, who beat Henry Maske to create the lineage. If you believe that Erdei vacated by moving up to cruiserweight and not fighting since, then you could easily argue that Pascal is the lineal champ, as he was the clear #2 guy when he beat the clear #1 guy in Chad Dawson.
Middleweight - No controversies here. Bernard Hopkins was the sole undisputed champ of the four belt era. Jermain Taylor beat him, then Kelly Pavlik beat Taylor, then Sergio Martinez beat Pavlik, making him the true champ.
Junior welterweight - If you think he hasn't vacated by not fighting there for a couple years (with no indication he'll ever drop back down), then it's Manny Pacquiao, who beat Hatton, who beat Tszyu, who beat Judah to create the lineage. Most people believe this is vacant.
Lightweight - Juan Manuel Marquez beat Joel Casamayor, who beat Chico Corrales, who beat Jose Luis Castillo to create the lineage. Even though Corrales lost the rematch to Castillo, he didn't lose the championship because Castillo failed to make weight.
Flyweight - This is by far the longest lineage. Pongsaklek Wonjongkam beat Kameda, who beat Naito, who beat Wonjongkam, to beat Tunacao, who beat Singsurat, who beat Pacquiao, who beat Sakasul, who beat Arbachakov, who beat Muangchai, who beat Chitalada, who beat Kim, who beat Chitalada, who beat Bernal, who beat Kobayashi, who beat Cedeno, who beat Magri, who beat Mercedes, who beat Castillo, who beat Cardona, who beat Avelar, who beat Oguma, who beat Park, who beat Canto, who beat Gonzalez to create the lineage. But Pongsaklek only recently became the Ring champ because of when the magazine ceased publication.
Light Fly - Giovanni Segura, who beat Ivan Calderon, who beat Hugo Cazares to create the lineage.