sir82,
What you say makes sense. Paul's writings came first, and he died before any of the gospels hit the shops. Since he was at loggerheads with the Jewish Christians at Jerusalem (they would not have been too excited at what he wrote about the Law to the Galatians and to the Romans), it is not unlikely that their writings were intended to counter his. Just see how legalistic Jesus is in their writings.
During the succeeding centuries, the various Christian sects remained at loggerheads, and a reason Paul is paramount in the writings they canonised lies in the fact that the emperors of the eastern Roman Empire selected the Pauline group, and thus created orthodoxy (but did not resolve the isssues).
Most likely Paul's ideas were selected because they were better accommodated to the Roman/Hellenistic philosophising than were the legalistic requirements (circumcision, etc.) of the Jewish Christians based at Jerusalem.
Doug