Federer is definately one of the greatest tennis player ever, but I don't think he's the most dominant. Like you said sampras is just as impressive as Federer was when he was in his prime.
Tiger is good, but until he wins more majors than Jack Nicklaus, I can't consider him as the most dominant golfer that ever played.
Jordan is one the best basketball player that ever played. However, stats wise, he's not that impressive compared to other players in different eras. I think Jordan change the way the game is played more than he was dominant.
I can see a case for shawn white. It seems like he always wins gold on super pipe and slopestyle. It's hard to judge right now because he's still young. If he continues to dominant then yes he is right up there.