Well your comparison considers that Casillas was a top level player who won more than anybody else in his position, which is what Puyol did. It doesn't say that Casillas is the best keeper of all time.
My top ten since I've been watching football (since around 1990, in no order):
Baggio, Romario, Ronaldo, Zidane, Luis Figo, Del Piero, Kakà, Ronaldinho, Cristiano Ronaldo, Messi.
That combination of acceleration, control and finishing was deadly, that's really all you need to be a great scorer. Lose one of those and you are talking about a good player, but not many can do it all.