I'm with splendidsplitter: well done and thanks.
Koufax, whom I did see pitch once in Philly, deserves the top spot. Gibson was great, no question, but a little mean for my taste--he loved brushback pitches even more when they hit someone. I hasten to add that was actually not that abnormal in his era. He was incredibly competitive.
My memory of Koufax is that he was not quite so competitive--at least in terms of brushback pitches--but in his prime had great stuff, especially his fastball and curve. He was elected to the Hall of Fame at age 36, the youngest ever because arthritis made him quit at age 30/31. In his three Cy Young (unanimously selected) years of 1963, 1965, and 1966, he started 40, 41, and 41 games and pitched 20, 27, and 27 complete games. 1966 was also his final year.
Until you put up his postseason stats (all World Series of course), I did not know he was so great in the postseason.