I grew up watching Robby Naish windsurfing vids too and admire the mans skills, however he is just as human as the other super talented humans you have never heard of...and where do you account for the evolving generations...gear/technology, number of opponents,
If, as some previous points suggest,(winning 12-13 world titles etc) you are looking for someone who has dominated a sport as much or more and during the early periods of a sport before it hit its peak in popularity, then check out Heather Mckay...Squash player and Australian field hockey player...
"Heather McKay, completely dominated the sport of women's squash in the 1960s and '70s. She lost only two matches in her entire career (in 1960 and 1962), and was unbeaten in competitive squash matches from 1962 through to 1981, when she retired from active open squash.
Winning 16 consecutive British Open titles (considered to be the effective world championship of the sport at the time) between 1962 and 1977, and capturing the inaugural women's World Open title in 1979, whilst remaining undefeated during that period. Heather also proved to be a talent in other sports, including field hockey, where she was a member of the Australian Women's Hockey Team in 1967 and 1971
In racquetball, she won the American Amateur Racquetball Championship once (1979), the American Professional Racquetball Championship three times (1980-81 and 1984), and the Canadian Racquetball Championship five times (1980 and 1982-85). She was inducted into the USA Racquetball Hall of Fame in 1997
en.wikipedia.org/wiki/Heather_McKayBut then again this is all just a wank fest and will always be personal opinion, so I say admire who you will and be done with it because there is probably someone else who has a supposedly comparative yet better record in some other sport/s....