Theology- "So God created man in his own image, in the image of God he created him; male and female he created them." (Genesis 1:27)
"There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female; for you are all one in Christ Jesus." (Galatians 3:28)
The above texts emphasise that both women and men are made in the image of God. One of the main arguments against the ordination of women is that women are not made in the likeness of Christ. Do not women show Christ like characteristics such as love, compassion, personal concern, nurturing, wisdom and sacrifice? What is essential is Christ's humanity not his maleness.
Tradition- The "received" tradition in the church of women as inferior has excluded them from the sacramental role of priesthood and from other decision-making roles. St. Thomas Aquinas' opinion that "woman is by nature in subjection (to men), but a slave is not (by nature in subjection)" seems to be shared by today's hierarchy.
Jesus did not ordain women- He did not ordain men either! This came later in the Church's history. Jesus called women as well as men to be his disciples. As the Pope's recent letter points out, Jesus went out of his way to include women among his disciples. The first apostle of all was the apostle to the Samaritans, the woman at the well. The first apostles of the Resurrection were Mary Magdalene and her friends. There were also many other apostles, women, appointed by the risen Christ.
(1 Corinthians 15:6)
Against women
1. The Saviour chose no women apostles and (so far as we know) commissioned no women to teach or exercise the power of the keys
2. St Paul forbade women to teach or have authority over men in the Church. Among other things, this suggests how St Paul interpreted the fact that Christ appointed no women apostles.
3. There were no women bishops or presbyters in the early centuries of the Church. This indicates that St Paul's take on the matter was not his personal opinion, but the consensus among the Apostles which was handed down to their successors.
4. In the third century, the principal point at issue between the Montanist heretics and the orthodox was the reliability of the Apostolic Tradition, compared to the "new revelations of the Holy Spirit" that the Montanists were claiming. One of the principal arguments against the Montanists was that their practice of ordaining women proved that they were not faithful to the Apostolic Tradition. This indicates that the ordination of men only to the presbyterate and the episcopate was part of the authentic teaching of the Apostles.
5. The canon law of the early Church specifically forbade the ordination of women to the presbyterate and episcopate. These canons were endorsed by the Council of Nicaea which gave us our Creed. You could say that Nicaea got the Apostolic Tradition wrong on this point, but they sure got it right in the Creed, so I don't think so.
You can interpret Scripture to allow women pastors, by attributing St Paul's strictures against it as either his personal opinion or as applicable only to his time and place. But there's a right way and a wrong way to interpret Scripture, and the consistent and specific understanding of Scripture on the part of orthodox Christianity through the centuries is a pretty reliable guide. Choosing one's interpretation to conform to current understandings of "equality" is not.