I agree, that may be the greatest single season ever for a pitcher. But it's also important to factor in the higher-mound era as a context. Juan Marichal actually had 2 more complete games that year (30). He averaged 8.6 innings per start, while Gibson averaged nearly 9. But again, I do agree. And of course, Koufax had an amazing run just prior to 1968
I believe Pedro Martinez had even better seasons during his amazing 5-year run. Pedro's era was more than a full run less than any other pitcher in baseball.