My wife likes to watch the seemingly never ending stream of Christmas movies every year that they show on the various channels (mostly Lifetime and Hallmark). I always poke fun and ask which of the plot lines it follows, since they are all based on only a few variations. For years I've asked her to categorize the plot lines and she hasn't, so this year I finally did it for her.
Now, Hallmark and Lifetime plot lines are different. The Hallmark movies are generally "happy/feel good" while the Lifetime plots are generally have some tragedy involved to make you cry.
All of these movies typically use 1 to 3 of these plot lines mixed together.
Standard "real-life" plot lines.
Single person A goes back to hometown during Christmas and meets "old flame" single person B. Their love is rekindled through the power of the "Christmas spirit(tm)"
A small town, person, or some other business entity is bankrupt, and another person is sent in to to manipulate or take advantage of the situation with various nefarious intentions, which are always later discovered. The person will typically finally realize they are doing "wrong" and repent in the end due to the "Christmas spirit(tm)".
Time travel, parallel universe, alternate life, or "wish granting" is experienced with return to reality and an epiphany at end that where they appreciate their original situation.
Person has lost "Christmas spirit(tm)" but regains it through an epiphany. The loss can be for many sub-reasons including the tragic death of family member, or that the family member is just too busy with career to participate in family Christmas events. Realizes in the end they are missing out. This includes all variants of "A Christmas Carol" and the "Scrooge" character.
Person A visits family for Christmas and hires, kidnaps, or just convinces person B to go with them to meet their family and act as their partner in order to avoid conflict or embarrassment. Of course, this always leads to "true love."
A marriage/couple/family is broken up through divorce, separation, or death. Consequently, their children, pets, or other family members help them rekindle their love, or find a new love, usually through memories of past Christmas holidays.
"Santa organization" related plot lines.
I define the "Santa organization" as Santa, Mrs. Claus, their children, some of the more sentient reindeer, and the upper-level Elven handlers that organize Christmas.
A marriage/couple/family is broken up (or has never met at all) and one or more members of the "Santa organization" help them meet or rekindle their love.
Santa is "retiring" and has to convince indifferent offspring to take over. Some variations occur where it is not the "real" Santa.
A member of the "Santa organization" goes to the real world for various reasons and must be returned in time for Christmas. Reasons may include retirement, a love interest, alternative career pursuits, or amnesia. In the case of retirement, for some reason Santa is required to be married. It is unclear to me why Santa must be married to fulfill his duties. Things always work out by Christmas eve, though.
The reindeer are injured, the sleigh is broken, or simply won't function anymore due to lack of "Christmas Spirit(tm)". It must be fixed before Christmas eve.
There is also the broad "General skit comedy involving families at Christmas." I hesitate to include this because this is a cheat and includes many movies that are not in the "Lifetime/Hallmark" style. However, sometimes this is combined with other elements in these movies. Examples- "Christmas Vacation", "Christmas Story", and of course "A Madea Christmas"