I see what you did there OP.
But anyway, Federer makes the game look easy and effortless, the biggest reason being his grace. Every other human being shouldn't be able to hit 100mph forehands and laser like backhands down the line while his perfect hair flows in the wind and his arms extend like a figure skater landing a triple axel. It's just not possible...it's almost not athletic, it's something else. Poetry maybe?
While Nadal and Djokovic and Safin and Sampras do incredible things and make them look routine there is certainly obvious effort and work and drive behind everything they do. Take Nadal's reverse forehand spin or Djokovic's running splits. Yes, they stretch the capability of the human body...but it's obvious they couldn't do that without years of physical exertion and dedication. Federer just looks like he was born that way.
There are things known, and things unknown, and in between are The Doors.