Great as in important,not great as in a good and noble man, he had some bad flaws too- kind of egomaniacal, and apparently was pleased with the segregation aspect of MLB. Yet he did a huge part to restore the integrity of the game after the 1919 scandal, and, while autocratic at times, he did make very important decisions on important issues ( he'd been a federal judge before) such as the role of minor league systems, and is the commisioner with the greatest power in that leadership role in baseball history.