[darwinbulldog]

Glad to find this thread. I've been putting together my own checklist of greatest ever by sport and have a pretty extensive list at this point. I've tried to include all the popular sports, even if they aren't popular in the U.S. I name just one if I think the choice is clear and everyone I consider a plausible candidate in cases where it just depends on what stats you want to emphasize.

Baseball: Ruth
Basketball (men's): Chamberlain/Abdul-Jabbar/Jordan/James
Basketball (women's): Catchings/Taurasi
American Football: Brady
Ice Hockey: Orr/Gretzky/Lemieux
Soccer (men's): Messi
Soccer (women's): Hamm/Marta
Boxing (men's): Robinson/Louis/Marciano/Ali/Tyson/Mayweather
Boxing (women's): Taylor
Tennis (men's): Emerson/Djokovic
Tennis (women's): Court/Navratilova/Graf/Williams
Golf (men's): Nicklaus/Woods
Golf (women's): Didrikson/Sorenstam
Softball: Fernandez/Richardson
Volleyball (men's): Kiraly
Volleyball (women's): Walsh
Cricket: Bradman/Tendulkar
Rugby: McCaw
Cycling: Merckx
Swimming (men's): Phelps
Swimming (women's): Ledecky
Gymnastics (women's): Latynina/Biles
Gymnastics (men's): Andrianov/Uchimura
Sprinting (men's): Bolt
Sprinting (women's): Fraser-Price
Middle distance (men's): Nurmi/Gebrselassie/Bekele/Farah
Middle distance (women's): Dibaba
Marathon (men's): Kipchoge
Marathon (women's): Radcliffe
Athletics, general (men's): Thorpe/Owens/Morris/Lewis/Mayer
Athletics, general (women's): Didrikson/Joyner-Kersee
Figure skating (women's): Henie
Figure skating (men's): Hanyu
Alpine skiing (men's): Stenmark
Alpine skiing (women's): Shiffrin
Nordic skiing (men's): Daehlie
Nordic skiing (women's): Bjorgen
Diving (men's): Louganis
Diving (women's): Minxia
Table tennis (men's): Long
Table tennis (women's): Yue
MMA (men's): Johnson/St. Pierre
MMA (women's): Nunes
Field hockey (men's): Chand
Field hockey (women's): Aymar
Wrestling: Karelin
Badminton (men's): Dan/Wei
Badminton (women's): Ling/Ning
Judo (men's): Nomura/Riner
Judo (women's): Tani
Weightlifting (men's): Süleymanoğlu/Alekseyev
Weightlifting (women's): Lian/Slivenko
Lacrosse (men's): Gait/Rabil/Powell
Lacrosse (women's): Cummings
Squash (men's): Khan
Squash (women's): McKay
Stock car racing: Petty
F1 racing: Hamilton
Skateboarding (men's): Hawk
Skateboarding (women's): Bufoni
Snowboarding (men's): White
Snowboarding (women's): Jacobellis
Surfing (men's): Slater
Surfing (women's): Beachley/Gilmore
Taekwondo (men's): Lopez
Taekwondo (women's): Kyung-Seon
Water polo (men's): Gyarmati
Water polo (women's): Steffens
Speed skating, short track (men's): Hyun-Soo
Speed skating, short track (women's): Fontana/Meng
Speed skating, long track (men's): Kramer
Speed skating, long track (women's): Karlijn Wuust
Sumo: Hakuho
Pool (men's): Reyes
Pool (women's): Balukas/Fisher
Horse racing, jockey: Shoemaker
Horse racing, horse: Man o' War/Secretariat