Okay I've got some more: Dave McNally, Harry Becheen, Lefty Williams, Sam McDowell, Johnny Vander Meer, and Bob Veale who were better than Pettitte and at least as good as Glavine and Newhouser.
I would take Koufax. Grove, and Carlton above Randy Johnson. Actually, probably Warren Spahn too if you look at his body of work. Grove, Carlton, and Spahn all did it for a long time, but at his peak, no one was better than Koufax. I was born in 1952 and grew up near St. Louis. Whenever the Dodgers played the Cardinals, Koufax pitced against Gibson. I watched then every chance I got and I knew when I was seeing it then I was seeing two of the best pitchers ever. It seemed to be always 1-0 or 2-1. In addition there may have been better hitters around then than any other time in baseball history.