Graham actually entered ministry before the Holy Father as I understand it - Wojtyla was not ordained until 1946 (in fairness, he would have been ordained sooner save that he was dodging Nazis). Graham began preaching in the 30's.
We can say both men devoted pretty much their whole adult lives to Christ. The chief difference is that much of Wojtyla's early ministry was confined to theological education and ministry in the Krakow archdiocese. Graham was not limited by any geographical boundaries.
That's just a reflection of the ecclesial differences between the Catholic and Baptist traditions.