Yes, Paul was not married during his entire ministry of preaching the Gospel of Jesus Christ. However, Before his ministry to gospel of Jesus Christ, Paul was a member of the Sanhedrin, and to be a member of the Sanhedrin, one is required to be married. I seriously doubt the Sanhedrin made an exception for Paul.
All the other Apostles were married. Jesus brothers were married, and most likely so was His sisters. Jesus never married, but He does have plans for marriage, and it involves us. He is the groom, we are the bride.
I see no added virtue that unmarried Christians have over married Christians. If any Christians choose not to marry, I wish them the well with their choice, but I do not see it as being more superior life choice than being Married, and with Children.
The other 12 Apostles were all married. Are they less Christian or lesser Apostles than Paul.
Jesus siblings, His brothers, and presumably Jesus sisters, born to Joseph and Mary, married.
In 1 Corinthians. Paul's first letter, Paul believed that the Great tribulation was imminent.
Paul's advice to not marry was predicated on the fact: that since the great tribulation was at hand, it would be very painful to see one's children and spouses suffer with a cruel death under the anti-Christ. And Paul made it clear that this was not from God, but his own opionion and concern.
Apparently, his 'time table' was off, as can be seen by the fact that the Great tribulation has not yet come. And it does seem that it may be very near, and may very well happen in our time. It sure looks like that way to me.