I assume this comment was made before the last Wimbledon, which showed a 14 percent drop in TV ratings in the US for the women's final. I think the Williams sisters have already lost some of their luster because they generally play such bad matches against each other.
Men's tennis has produced much better tennis in the last couple of years. Unfortunately, the players on the men's side are not very colorful.
But other players on the women's side were just as colorful as the Williams sisters and fyi, Tiger Woods has not won a major in his last six tries. Its usually a mistake to bet the farm on any single athlete in any sport.