New Age horsefeathers. The four canonical gospels were recognized long before 325, and Constantine had nothing to do with that decision.
Other parts of the New Testament canon were "in play" as late as AD 400, but not the Gospels, and not most of the Pauline epistles, either.
True. Don't have the references here, but I recall the first authoritative listing of what would become the cannon of the New Testament being in a Christmas letter sent out by one of the apostolic church bishops some time in the 2nd century A.D.
As for Constantine, he had a tremendous influence on the development of institutional Christianity by: 1) stopping the persecution of Christians, 2) by proclaiming official tolerance of the religion, 3) by adopting it as the official and only religion of the Roman Empire and finally, 4) by sponsoring a series of conferences to bring together church leaders and regularize Christian doctrine and practice. Whether or not the long partnership between church and state has been for good or for bad is the subject of a centuries-long discourse and many books.