Ah, the Pope -- the Bishop of Rome. For Catholics, Head of the Church. For many others (regardless of religious faith -- if any) a respected world leader. For some, a symbol of evil! In any case, the Papacy has provided the history of the world with some very interesting characters: many saints, some scandals, all sinners.
Here are the Popes who have served in that office for the longest period of time. Please note although St. Peter spent time in Jerusalem and Antioch before coming to Rome. His dates are, of necessity, approximate.