The centrality of St. Paul to the Church is beautifully described in this talk by Pope Benedict.
An excerpt.
“The saint's martyrdom, said the Holy Father, "is first related in the 'Acts of Paul' written towards the end of the second century. They state that Nero condemned him to be beheaded, and that the execution was summarily carried out. The date of his death varies in the ancient sources, which place it between the persecution unleashed by Nero following the fire of Rome in summer 64, and the last year of his reign, 68". According to tradition he was beheaded at a place in Rome known as "Tre Fontane" (Three Fountains), and buried on the Via Ostiense, where the basilica of St. Paul's Outside-the- Walls, erected over his tomb, stands today.
"In any case", he went on, "the figure of St. Paul towers over the events of his earthly life and death. He left an extraordinary spiritual heritage. His Letters soon entered the liturgy where the structure: Prophet-Apostle-Gospel would prove decisive for the form of the Liturgy of the Word. Thanks to this 'presence', ... the Apostle has been, since the very start, spiritual nourishment for the faithful of all times".
"The Fathers of the Church, and later all theologians, drew sustenance ... from his spirituality. For this reason he has, for centuries, been the true Master and Apostle of the Gentiles. ... To him St. Augustine owes the decisive step in his own conversion, and St. Thomas Aquinas left us a magnificent commentary on his Letters, the finest fruit of medieval exegesis. Another decisive moment was the sixteenth-century Protestant Reformation", when Luther "found a new interpretation for the Pauline doctrine of justification which freed him from scruples and concern ... and gave him a new and radical trust in the goodness of God, Who forgives everything unconditionally. From that moment Luther identified Judeo-Christian legalism - condemned by the Apostle - with the life of the Catholic Church, while the Church herself appeared to him as enslaved to the Law, with which he contrasted the freedom of the Gospel.
"The Council of Trent", the Holy Father added, "provided a profound interpretation of the question of justification and found, in line with all Catholic tradition, a synthesis between the Law and the Gospel, in conformity with the message of Scripture considered in its entirety and unity.
"The nineteenth century, drawing on the finest elements of Enlightenment tradition, saw a fresh revival of Pauline studies in the field of academic research, of historical-critical interpretation of Sacred Scripture. ... The new Paulinism of that century considered the concept of freedom as a central part of the Apostle's thought, ... and he is presented almost as a new founder of Christianity. What is certain is that in St. Paul the centrality of the Kingdom of God ... is transformed into the centrality of Christology, the decisive moment of which is the Paschal Mystery whence derive the Sacraments of Baptism and the Eucharist, as a permanent presence of this mystery thanks to which the Body of Christ grows and the Church is constructed".
“Over the last two hundred years in the field of Pauline studies "there has been increasing convergence between Catholic and Protestant exegesis, and conformity is being discovered on the very point that gave rise to the greatest historical disagreement. This represents a great hope for the cause of ecumenism, so fundamental for Vatican Council II".