Let’s say top 3 at least if we count by age brackets. Without internal order I’d guess these are the top 3 of different generations/age groups. Doesn’t fit perfectly but close enough
80-85 Rocks, Kong, …
75-80 Roger, Garp, Rayleigh
70-75 Whitebeard, Shiki, Big Mom
65-70 …
60-65 …
55-60 Dragon, Akainu, Kaido
50-55 Aokiji, Fujitora, Beckman
45-50 King, Katakuri, Marco
40-45 Mihawk, Shanks, Blackbeard
35-40 …
30-35 …
25-30 Kidd, Law, Yamato
20-25 Zoro, Sabo, …
15-20 Luffy, Coby, …
10-15 Bonney, …, …
Looks like there are some ”lost generations”, probably due to it being close to impossible to rise following some of the strongest generations. If you want to expand you could add Hancock and so on but you get the general jist of it.