A clarification:
Koufax won five straight ERA titles, but that was five straight National League ERA titles, 1962, 1963, 1964, 1965, and 1966. He led all of MLB in ERA in only three of those years, 1963, 1965, and 1966. Koufax was 30 years old the day that the 1966 season ended.
Kershaw is going to lead all of MLB for four consecutive years, 2011, 2012, 2013, and 2014, as soon as the official figures for 2014 are complete. Kershaw is only 26 years old. He has not yet reached his peak.
Personal note: In 1965, when I was 15 years old and the Dodgers had just won the World Series for the fourth time in my young lifetime, I made no distinction in my mind between Sandy Koufax and God. Being older now and much more mature, even if Kershaw pitches a shutout to win the 7th game of the World Series (as Koufax did in 1965), I will fully understand that he is just a very talented human being.