Wladimir Klitshcko
He holds 2 of the 4 major world titles (IBF and WBO) and is recognized by Ring Magazine as the Heavyweight World Champion.
This question is not as simple as it had been in years past, due to there now being 4 major organizations (WBA, WBC, IBF, and WBO) who recognize world champions with the awarding of a title belt. In 1983 the IBF came into existence and the WBO did in 1988. However, the WBO did not gain major recognition until the mid to late 1990's.
Currently the WBC title holder is Vitali Klitschko (the older brother of Wladimir). The WBA title holder is David Haye.
Jack Johnson
rocky balboa
Jack Johnson
Joe Louis...
martin martin
He was world heavyweight boxing champion from 1952 until his retirement in '56.
Joe Louis was World Heavyweight Champion from 1937 to 1949.
idi amin, believe it or not.
Rocky Marciano
The one and only Rocky Marciano.
Chris Archiballs. Great fighter from the mean streets.
Idi Amin Dada