For nearly two decades, The Hallmark Channel completely dominated the fusion of romantic comedies with Christmas movies. This season, however, Netflix’s digital platform has tried to appropriate this subgenre with the simultaneous release of “Our Little Secret,” “The Merry Gentlemen” and “Hot Frosty.” None of the three productions have the same plot, but each tries to find new ways to recycle conventions that provide romantic fantasies accompanied by the more superficial parts of what Christmas celebration entails.