I think this theory that everyone has about "Koreans being better than foreigners" is a stupid theory with no real logic behind it, other than the evidence of Koreans winning most major tourneys. But that doesn't mean that "Koreans" are the better SC2'ers, it means that a player, who happens to be a Korean, practices harder, trains harder, calculates things better and analyses things better then his opponents.
I beleive it is the pure dedication from players, who happen to be Korean, that makes them better. They spend their entire lives hammering the game and exploring and exploiting every inch o f the game they can. Look at Jinro in season 1 and 2 of GSL. He fucking DOMINATED because he practiced like 24/7. And now HuK, who plays SC2 for more than 60% of every day, now he is pretty dam good. And the recent anihilation of the Swedes in GSL Code A isn't due to Koreans being imba, it's due to extreme nerves and completely different play-style catching the Swedes off guard.
That's my opinion anyway.