Look up any list of greatest fighters that ever lived, no doubt you will find a mixture of different fighters from different weight classes. On many occasions, numbers 2-10 on those lists may vary dramatically, but the No. 1 spot is rightly secured in most of them by none other than the welterweight Sugar Ray Robinson.
One can't say how a fighter from one weight class would have done at another division had he been bigger or weighed less. Those imaginations and comparisons are what lead us to the popular concept of the pound-for-pound rankings in which Sugar Ray Robinson also ranks No. 1 of all-time.
In this list we go away from the concept of pound-for-pound rankings and look back and give credit to the best fighters than each division ever produced.