This is from the TAC, of Thomas Aquinas College website. Look here for more quotations from other popes. http://www.thomasaquinas.edu/a-liberating-education/popes-st-thomas
1. Pope John XXII, speaking about St. Thomas, said before his canonization that “his life was saintly and his doctrine could only be miraculous … because he enlightened the church more than all the other doctors. By the use of his works a man could profit more in one year than if he studies the doctrine of others for his whole life.”
4. Leo XIII stated that “this is the greatest glory of Thomas, altogether his own and shared with no other Catholic Doctor, that the Fathers of Trent, in order to proceed in an orderly fashion during the conclave, desired to have opened upon the altar together with the Scriptures and the decrees of the Supreme Pontiffs, the Summa of St. Thomas Aquinas whence they could draw counsel, reasons and answers.”
Again from Leo XIII: “This point is vital, that Bishops expend every effort to see that young men destined to be the hope of the Church should be imbued with the holy and heavenly doctrine of the Angelic Doctor. In those places where young men have devoted themselves to the patronage and doctrine of St. Thomas, true wisdom will flourish, drawn as it is from solid principles and explained by reason in an orderly fashion … Theology proceeding correctly and well according to the plan and method of Aquinas is in accordance with our command. Every day We become more clearly aware how powerfully Sacred Doctrine taught by its master and patron, Thomas, affords the greatest possible utility for both clergy and laity.
5. St. Pius X said that the chief of Leo’s achievements is his restoration of the doctrine of St. Thomas. For he “restored the Angelic Doctor … as the leader and master of theology, whose divine genius fashioned weapons marvelously suited to protect the truth and destroy the many errors of the times. Indeed those principles of wisdom, useful for all time, which the holy Doctors passed on to us, have been organized by no one more aptly than by Thomas, and no one has explained them more clearly.” Indeed, Pius said, those who depart from the teaching of St. Thomas “seem to effect ultimately their withdrawal from the Church … As we have said, one may not desert Aquinas, especially in philosophy and theology, without great harm; following him is the safest way to the knowledge of divine things.… If the doctrine of any other author or saint has ever been approved at any time by us or our predecessors with singular commendation joined with an invitation and order to propagate and to defend it, it may be easily understood that it was commended only insofar as it agreed with the principles of Aquinas or was in no way opposed to them.” Theology professors “should also take particular care that their students develop a deep affection for the Summa … In this way and no other will theology be restored to its pristine dignity, and the proper order and value will be restored to all sacred studies, and the province of the intellect and reason flower again in a second spring.”
7. Pius XI said that “indeed, We so approve of the tributes paid to his almost divine brilliance that we believe Thomas should be called not only Angelic but Common or Universal Doctor of the Church. As innumerable documents of every kind attest, the Church has adopted his doctrine for her own.… It is no wonder that the Church has made this light her own and has adorned herself with it, and has illustrated her immortal doctrine with it … It is no wonder that all the popes have vied with one another in exalting him, proposing him, inculcating him, as a model, master, doctor, patron and protector of all schools … Just as it was said of old to the Egyptians in time of famine: ‘Go to Joseph, so that they should receive a supply of corn to nourish their bodies, so to those who are now in quest of truth We now say: ‘Go to Thomas’ that they may ask from him the food of solid doctrine of which he has an abundance to nourish their souls unto eternal life.”
8. Bl. John Paul II said: “[T]he Church has been justified in consistently proposing Saint Thomas as a master of thought and a model of the right way to do theology….
“[T]he Magisterium has repeatedly acclaimed the merits of Saint Thomas’ thought and made him the guide and model for theological studies.… The Magisterium’s intention has always been to show how Saint Thomas is an authentic model for all who seek the truth. In his thinking, the demands of reason and the power of faith found the most elevated synthesis ever attained by human thought, for he could defend the radical newness introduced by Revelation without ever demeaning the venture proper to reason.”
9. Pope Benedict XVI said, “In his encyclical Fides et Ratio, my venerated predecessor, Pope John Paul II recalled that ‘the Church has been justified in consistently proposing St. Thomas a master of thought and a model of the right way to do theology’ (No. 43).
“It is not surprising that, after St. Augustine, among the writers mentioned in the Catechism of the Catholic Church, St. Thomas is quoted more than any other — some 61 times! He was also called the Doctor Angelicus, perhaps because of his virtues, in particular the loftiness of his thought and purity of life.
“In short, Thomas Aquinas showed there is a natural harmony between Christian faith and reason. And this was the great work of Thomas, who in that moment of encounter between two cultures — that moment in which it seemed that faith should surrender before reason — showed that they go together, that what seemed to be reason incompatible with faith was not reason, and what seemed to be faith was not faith, in so far as it was opposed to true rationality; thus he created a new synthesis, which shaped the culture of the following centuries.”