Objection 1. It would seem that virginity is the greatest of virtues. For Cyprian says (De Virgin. [De Habitu Virg.]): "We address ourselves now to the virgins. Sublime is their glory, but no less exalted is their vocation. They are a flower of the Church's sowing, the pride and ornament of spiritual grace, the most honored portion of Christ's flock."
Objection 2. Further, a greater reward is due to the greater virtue. Now the greatest reward is due to virginity, namely the hundredfold fruit, according to a gloss on Matthew 13:23. Therefore virginity is the greatest of the virtues.
Objection 3. Further, the more a virtue conforms us to Christ, the greater it is. Now virginity above all conforms us to Christ; for it is declared in the Apocalypse 14:4 that virgins "follow the Lamb whithersoever He goeth," and (Apocalypse 14:3) that they sing "a new canticle," which "no" other "man" could say. Therefore virginity is the greatest of the virtues.
On the contrary, Augustine says (De Virgin. xlvi): "No one, methinks, would dare prefer virginity to martyrdom," and (De Virgin. xlv): "The authority of the Church informs the faithful in no uncertain manner, so that they know in what place the martyrs and the holy virgins who have departed this life are commemorated in the Sacrament of the Altar." By this we are given to understand that martyrdom, and also the monastic state, are preferable to virginity.
I answer that, A thing may excel all others in two ways. First, in some particular genus: and thus virginity is most excellent, namely in the genus of chastity, since it surpasses the chastity both of widowhood and of marriage. And because comeliness is ascribed to chastity antonomastically, it follows that surpassing beauty is ascribed to chastity. Wherefore Ambrose says (De Virgin. i, 7): "Can anyone esteem any beauty greater than a virgin's, since she is beloved of her King, approved by her Judge, dedicated to her Lord, consecrated to her God?" Secondly, a thing may be most excellent simply, and in this way virginity is not the most excellent of the virtues. Because the end always excels that which is directed to the end; and the more effectively a thing is directed to the end, the better it is. Now the end which renders virginity praiseworthy is that one may have leisure for Divine things, as stated above (Article 4). Wherefore the theological virtues as well as the virtue of religion, the acts of which consist in being occupied about Divine things, are preferable to virginity. Moreover, martyrs work more mightily in order to cleave to God--since for this end they hold their own life in contempt; and those who dwell in monasteries--since for this end they give up their own will and all that they may possess--than virgins who renounce venereal pleasure for that same purpose. Therefore virginity is not simply the greatest of virtues.
Reply to Objection 1. Virgins are "the more honored portion of Christ's flock," and "their glory more sublime" in comparison with widows and married women.
Reply to Objection 2. The hundredfold fruit is ascribed to virginity, according to Jerome [Ep. cxxiii ad Ageruch.], on account of its superiority to widowhood, to which the sixtyfold fruit is ascribed, and to marriage, to which is ascribed the thirtyfold fruit. But according to Augustine (De QQ. Evang. i, 9), "the hundredfold fruit is given to martyrs, the sixtyfold to virgins, and the thirtyfold to married persons." Wherefore it does not follow that virginity is simply the greatest of virtues, but only in comparison with other degrees of chastity.
Reply to Objection 3. Virgins "follow the Lamb whithersoever He goeth," because they imitate Christ, by integrity not only of the mind but also of the flesh, as Augustine says (De Virgin. xxvii). Wherefore they follow the Lamb in more ways, but this does not imply that they follow more closely, because other virtues make us cleave to God more closely by imitation of the mind. The "new hymn" which virgins alone sing, is their joy at having preserved integrity of the flesh.
Source: Summa Theologica (New Advent)