I mean he will win all grand slams including French Open, which Sampras NEVER reached the SEMI-final.

Why? Because clay court can absorb Sampras’ power, especially the strength of his powerful serve. Most of this forehand is flatstroke, which is very, very useful on grass court. But on clay court, without topspin is more effective, can let ball jump very high and far away.

"網球在被老桑焚書坑儒" -- I agree.
When you watch tennis game, would you just like to see the big serve, which most players can't return it? That's why the rules for serving in table-tennis have been changed!!! Now, tennis association is trying to let the ball become soft, reducing the speed of big serve. Please don't tell me you enjoy watch William sisters' play. That's a tennis disaster!!!

Federer's tech is similar to Agassi's. His backhand (single) is even better than Agassi double-backhand, covering more area with less running. And he is not affarid of moving to the net. He can play in different kind of courts. He will be the king in next few years.