Phelps is so far the best swimmer history has recorded and measured, as far as I can tell.

Does that make him the best olympic athlete? Recall that the last major winner of many medals in one year was a swimmer.

This indicates that there may be far too many awards for swimmers, not that swimmers are in some way the best athletes.

What if there were events for shooting a pistol with the right and left hands, upside down, sitting, standing, kneeling, crouching, ... maybe the best pistol shot in the world could get 20 medals. Does that make him a greater olympic athlete than, say, the best sprinter or the best shotputter?

Or does it just mean the whole system is an arbitrary game?

Really, what it means is that Phelps is the best swimmer of his generation, and perhaps of all time. Comparing the athletes of different sports is a fools errand. Swimming obviously offers more opportunities for success, or failure, then a team sport. Who is a better athlete, Phelps or Kobe Bryant? It is an impossible question to answer with any real objective standard.

At the end of 20th Century, Sports Illustrated declared Mohamed Ali as the greatest athlete of the Century. It was a silly proclaimation. Best Boxer, sure, why not. But best athlete? Was he the fastest runner? No. Was he the strongest person? No. The criteria used in the selection was highly suspect, and included social and political aspects that had nothing to do with athletics.

Let's just enjoy Michael Phelps accomplishments for what they acctually represent. The Tiger Woods like domination of a sport.

What if he wasn't an American how many of his medals are Relay wins? If he was from a weak swimming nation he wouldn't have won gold in those.

Not to argue semantics. Well, actually, exactly to argue semantics. It was best athlete but greatest athletethat SI crowned Ali with. While best really only speaks to ability and it is very hard to compare the apples and oranges of diverse sports as you pointed out, greatest deals with fame, social placement, etc.

And at the time of that story, Ali was inarguably the greatest athlete of the century, having touched either positively or negatively literally with his fame. It was hard to not know someone who didn't know who Ali was. And that is exactly what they were and still talk about when they speak of greatest. Fame and Influence.

What Phelps does outside the pool is going to shape his legacy as much as what he just did in it.

Ali was the greatest......draft dodger of all time.