The short answer is no, not all Popes became Saints after their death. In total, there have been 265 Popes, including Pope Emeritus Benedict XVI. Of those 265 Popes, less than a third (78) are Saints, most of these in the early centuries of the Church; many were martyrs. A further eleven have been named blessed (an intermediate step toward Sainthood), with Pope John Paul II’s recent beatification.
In 1588, the modern Sainthood process the Vatican now follows, began. When Pius X, who died in 1914, was made a Saint in 1954, he was the first Pope so honored in almost 400 years. Pope John Paul II received his blessed recognition exactly six years and 29 days following his death largely due to the papal exemption (waived by Pope Emeritus Benedict XVI) that five years must pass between a person’s death and the opening of his or her Sainthood cause.
Do all Popes become Saints after their death? was written by Kathryn Whitaker on Electing the Pope