I only started watching tennis in 2002, after the US Open. It was the sisters who sparked my interest in the game. There was so much excitement in the media, after they competed against each other in a GS final for the fourth time. The first match I watched featured Serena, and I've been addicted to tennis ever since. To be honest, I am a much bigger fan of Serena's than Venus', because, as mentioned, she has this intensity about her and a determination to win.
Great thread, btw.