My favorite line from any of them is from the Jordan vs Ali one - "your whole nba career turned whack when you came back a wizard like gandalf the black"
This is my favorite one due to the last line "I'd beat you in round two but that would be unbelievable because no one in your family lives to see a sequel."
[video=youtube;eHCyaJS4Cbs]
Most of these are damn funny, the new Wierd Al, Charlie 2na one i'v seen a ton but the best ones are probably the Darth Vader vs Adolf Hitler ones.