I know it makes me a bad person but I've never felt, FROM WATCHING HIGH LEVEL PLAY, that Guile was nearly as bad a MU Gief as is portrayed. Yes, I'm speaking purely from observation, but at the higher/est levels of play, I just don't see it as the 8/2 roflstomp that it's widely considered. I watch sets regularly and even the Japanese Guile/Gief masters go pretty tight.
Guile has amazing tools to keep Gief away but one mistake from Guile or solid read from Gief and Gief will run away with the round.
Guile absolutely wins the MU, but his margin for error is very small, very very small, at the highest levels of play. Below that where 99% of gameplay takes.place though, Guile shits on Gief HARD.