season in history for ERA+ (ERA adjusted for ballpark). The only pitchers in the last 40 years on this list ahead of him are Greg Maddux and Pedro Martinez (each twice). Arietta is having an amazing year, 86th all time in adjusted ERA this year, but not in the same ballpark as Greinke this year and also behind Sonny Gray (80th). Plus you continue to lose credibility with your wins argument.
http://www.baseball-reference.com/leaders/earned_run_avg_plus_season.shtml