1970 Joe Frazier 1971 Joe Frazier 1972 Muhammad Ali 1973 George Foreman 1974 Muhammad Ali 1975 Muhammad Ali 1976 George Foreman 1977 Ken Norton 1978 Larry Holmes 1979 Larry Holmes 1980 Mike Weaver 1981 Larry Holmes 1982 Larry Holmes 1983 Larry Holmes 1984 Pinklon Thomas 1985 Michael Spinks 1986 Mike Tyson 1987 Mike Tyson 1988 Mike Tyson 1989 Mike Tyson 1990 Evander Holyfield 1991 Evander Holyfield 1992 Riddick Bowe 1993 Evander Holyfield 1994 George Foreman 1995 Riddick Bowe 1996 Evander Holyfield 1997 Evander Holyfield 1998 Lennox Lewis 1999 Lennox Lewis
1991 is highly controversial, Holy looked really average against Cooper and Foreman, Tyson won against a more highly regarded rival at that time. 1997 Holy definitely looked better than Lewis. I have no opinion on Weaver and Thomas, but in my opinion Holmes in 1st place would not be a mistake. There are years when there was no clear leader. But, for example, George Foreman in 1973 or Mike Tyson in 1988 completely dominated, while 1994 could have been practically vacant, there was no one who could be considered a real champion.
Well, there were 3 real champions in 1994: Evander Holyfield, Michael Moorer and George Foreman. Lennox and then McCall were just a paper titlists. But it has nothing to do with who was the top heavyweight. I would say, the lineal unified champion should have the strongest claim, but overall, who had the better year? Hard to tell. The two best wins of the year was Moorer vs Holyfield and Foreman vs Moorer. You can add McCall's win against Lewis too. But Foreman and Moorer only had these 2 wins in a year. McCall had wins against Lewis and Larry Holmes, who wasn't ranked but regarded highly. I would still say Foreman's win against Moorer is the best one and since he didn't lose during the year (unlike Moorer), he would take the spot of the best heavyweight of 1994. EDIT: well, McCall win against Holmes came in 1995, so it's not much of a debate now.