Many of boxing's all time greatest pound-for-pound fighters spent significant time in their careers fighting in the middleweight division. Given the relatively high percentage of the male population that fits the middleweight frame (with strict training and dieting), it shouldn't be surprising that the talent pool at 160 pounds has been so deep over the years.
The heavyweight division will always be the larger than life glamor class (well, it would be if somebody would show heavyweight championship fights in the USA) and the smaller fighters often thrill us with blurring speed and relentless action. But boxing fans know that some of the most electrifying combinations of speed, athleticism and power happen in the middle.
Lists like these are intended to stimulate debate, so please use the comment section to let me know anybody you think I left out or anybody who should be ranked differently within.