Serena is more popular than Venus, but not according to the commentators. In fact, if you check them both out on social media you'll see that Serena eclipses Venus in every outlet. There is very little press on Venus, but the commentators would have the fans believe otherwise. They don't like Serena and didn't like Venus either until Venus began to lose, then they could tolerate her better. Remember how they used to call them both unfocused and lazy, but have been forced to eat their words considering their longevity in the sport.
Recently, Navriltilova accused Serena of being on drugs during her Wimbledon episode. When do they do that? Make baseless accusations that could damage a player, and let's not forget Chris Evert's "open letter" to Serena about how she was disrespecting the sport.
They don't like Serena because she is unapologetic, or should I say "uppity"? Venus, OTOH is more docile. Mystery solved.
I am actually neutral to both sisters. I remember in my CNN days in the late 90s, when both sisters had just turned pro, Venus was more popular as she was more successful than her sister at that early stage of their career. But since Serena has taken over her sister and won many more Slams than her sister, she's definitely more popular than Venus now. Serena, though, has her on court antics and not the good kinds. Her outburst at the AO not so long ago is a prime example and it wasn't particularly pretty. And there are few other incidents as well and perhaps that's why she's a less popular figure for the women commentators especially in the US.
One of the reasons Andy (even Tsonga is more popular than him I am afraid but then again I can't explain Fognini who's an utter tool oncourt and yet a lot of fans dig him) is least popular among top players is because of his on court behaviour. While he'd never act like Serena as she did with linepersons, referees, ballboys etc., the fact he berates himself on court and shouts at his box, does diminish his appeal and his popularity as a player. Federer used to be very angry at the early stage of his career however, once he started winning a lot and the fact that he idolized Sampras a great deal who was cool as cucumber, made him cool off a lot. But I don't see that either Serena or Andy doing that - reasons why Serena thinks they are a lot alike. They like being who they are even when sometimes they are wrong. I do like Serena's bubbly personality however and I accept the way Andy is though I am sure Andy would benefit much more if he cools off and not let anything bother him. Having a complete control over your emotion is the hardest thing perhaps but it's so worth it.