To the original OP. What makes him the best?
His power, finesse, use of the entire court, speed, acute angles he hits, mental toughness, flat forheands, footwork, flat backhands, squash forehands, slice backhands, volleys, top spin backhands, overheads, top spin forehands, serve, approach shots, return of serve, etc. etc etc.
Oh, and he does all of the aformentioned better than anyone else.
Roger Federer Pro Staff 97 Play test video