Starting pitching is a monster. I'm tempted to break it up into groups: pre-1910, pre-1969, and 1969 forward. Instead I'm going to keep them grouped as one, probably unfairly favoring pitchers from the modern era.
Roger Clemens
Walter Johnson
Cy Young
Christy Mathewson
Tom Seaver
Lefty Grove
Randy Johnson
Greg Maddux
Pete Alexander
Warren Spahn
Kid Nichols
Bob Gibson
Pedro Martinez
Steve Carlton
Phil Niekro