A couple years ago I took a world religions class at college. The teacher was a Philosophical Daoist (you need balance in life, ying yang, take the easy way). While explaining the history of Christianity she said that if it weren't for Paul, Christianity would have died. He was very passionate, spread the Gospel to most of the non-Jewish, and wrote most of the New Testament.
Naturally this irked me. Whether her point is valid or not is another story. On the one hand, it is significant that most of our New Testament was written by one man (though the gospels were not Paul), and that most of the evangelism to the non-Semitic world happened through the same man (or so it would seem). However, I would like to make a few points of explanation. I don't think this completely wraps up the concern, but it should remove most reasonable doubt.
1) Paul was not the only evangelist. Possibly in fact he is responsible for less than half of it (which is still a lot). All the apostles save John died martyrs for the faith. Peter was the rock center of the church and at one point was so touched by the holy spirit that sick were healed by even his shadow falling on them (Acts 5:15). Peter is responsible for the birth of the Coptic (Egyptian) church through teleporting to the Eunuch in Acts 8 and Thomas died in India (according to an Apocryphal book "The Acts of Thomas"). Other non-apostles were doing work at the time as well. Note Barnabas who split from Paul, presumably doing his own ministry. In his letter to the Corinthians, Paul mentions 'Apollos' as another evangelist too and does not seem to denounce him.
2) The reason we have so much on Paul is because he wrote it down (directed by the Holy Spirit and intended for the bible). We do not say that Herodotus and Homer (Histories, Illiad and Odessey) were the pillars of Greek culture, much less that without them it would have collapsed, simply because their works are the main ones that survive. Although they are not canonical and may not be accurate, we do have dozens on different books from different authors around the time - commentaries and letters and such, disciples of the apostles and other church leaders like Polycarp (if I remember correctly).
3) Paul wrote 13 of the 27 books of the New Testament. Romans was written by Luke, closely associated with Paul but not authored by Paul.
4) The fact that Paul wrote so many books may be a function of his giftings and situation rather than his zeal. Other people like Peter, John or James may have even been more passionate, but demonstrated it in different ways. Peter was the rock on which Jesus built the church, and may have been caught up in administration and leadership. John was more prophetic. Paul, on the other hand, was extremely learned, one of the Jewish upper class. He knew how to write and how to write well, how to make arguments from old testament scripture and how to reason. He was also itinerant and had a wide base of churches he wished to disciple, making letters one of the most practical ways to do so. The apostles in the near region of Israel may have had an easier time and not had to write so much, and had gifts of leadership rather than teaching.
5) I'll leave you with an argument from scripture itself: Acts 5: 35-39 "35 Then he addressed the Sanhedrin: “Men of Israel, consider carefully what you intend to do to these men. 36 Some time ago Theudas appeared, claiming to be somebody, and about four hundred men rallied to him. He was killed, all his followers were dispersed, and it all came to nothing. 37 After him, Judas the Galilean appeared in the days of the census and led a band of people in revolt. He too was killed, and all his followers were scattered. 38 Therefore, in the present case I advise you: Leave these men alone! Let them go! For if their purpose or activity is of human origin, it will fail. 39 But if it is from God, you will not be able to stop these men; you will only find yourselves fighting against God.”
