Well that's very much an opinion. But, currently Roger Federer is number and has been for a while. He's proven pretty unbeatable in recent contests. You can read up about players and their rankings at www.atptennis.com .
On the women's side of things, there hasn't been one player that's been dominating. Currently, Amelie Mauresmo is ranked number one, but there are a lot of great women on the court today. Clijsters and Henin-Herdenne have been looking very good recently as well.
That's a very tough question, and I'm sure people would disagree with me. Let's hear some other people's thoughts as well!
