Pedro's 1997-2000 is probably the best I'll ever see a pitcher do it. And that is fully acknowledging Clemens' ridiculous output (insert PED opinion here), The Big Unit, and Maddux's elegant brilliance.
Like Pedro's 1.74 ERA led the majors by almost a full run. Kevin Brown was 2nd at 2.58. In the American League, Pedro was almost 2 full runs clear of 2nd place! (Clemens 3.70). Clemens was closer to 34th place among qualified AL starters than he was to 1st!