I recently did an exercise for my own benefit, ranking the top 20 in each decade, a fighter only to appear in their best decade(IMO) but based on total career, Not quite the same as this question but I was amazed at the depth of the 80s. So, on the criteria of overall depth of fighters, and with my qualifiers, I rank them thus; 80 90 60 70 10 00 2020's too early to rate but will be high.
I find it hard to rank the bottom half of heavyweight lists, but I think you've nailed it perfect, mate.