Is he the greatest Olympian ever?

Probably yes.

And he comprehensively knows 'how to win'. I saw live the race where he won his 7th gold, he was no where in the top half of the swimmers at the turn at 50m, but still he managed to win. In fact, the serbian swimmer Cavic was winning till 50.50 seconds; the race got over at 50.58 seconds with Phelps winning. The commentator rightly pointed out why Phelps won: "He surged his hands towards the wall 'above' the water while others did it under water. This is the only reason for Phelps to win with a margin of one-hundredth of a second. And, most importantly he knows how to win". Just happy to witness history getting created. Probably this is the most happening sporting season with the epic Nadal-Federer Wimbledon final, the arrival of a mystery spinner and indeed Phelps at Beijing.