Honestly, the average person knows who Serena Williams, Venus Williams, and Maria Sharapova are. They might know who Andy Roddick and Roger Federer are, but not for sure.
Men's tennis as a sport isn't that special to the average person. There is the NBA, MLB, NFL, NHL, etc. which are based more on athleticism than technique. Obviously, if you play tennis, you'll probably watch it, but not the average sports fan.
Women's tennis is special. It is by far the best sport for women to play and it is impressive to see female athletes like 5'5" Justine Henin Hardenne crush the ball.
Also, women's tennis is NOT like minor league baseball to the MLB. That is really a ridiculous comparison. It is more like college basketball to the NBA. It is a totally different game with a totally different feel. Lots of people prefer college basketball to the NBA, even though the NBA is a higher level.
I am a huge tennis fan, and I definitely love both.