The Klitschko brothers legitimised the WBO . Vitali in 1999. And Wladimir in 2000. But they only used it as springboard to get some recognition. In 1996 they turned down Don King and they only wanted to fight in Germany. So the WBO was the only belt they could get a shot at til 2003 in Vitali's case and 2006 in Wladimir's case. Everybody talks about the value of the 4 belts. The WBO is always the least respected. Even if the champion may be the best at that weight. For example possibly Crawford and Kovalev.