I will vote for facebook for their ability to adopt with user generated contents which attracts much more people to stay close socially!
Well depends on what purpose. For socializing the best is Facebook, and for generating traffic the best is twitter followed by Digg
Hi guys i agree with you facebook , twitter,stumbleupon these all are the best sites for social networks
Currently I agree that FB is on top. It has certain unique features which make it different from others. But I still love Myspace