The original Miracle on 34th Street, which I believe NBC should always show on Thanksgiving Day, in the evening after the Macy's Thanksgiving Day Parade, since it centers around Macy's and the parade.
I also like It's a Wonderful Life, which I first discovered during my teenage years, when it was on our local PBS station before it became popular again. Many people do not realize that it had fallen into obscurity and the copyright was lost, which actually helped it to become popular again. TV stations could show it for free, and so many did. That lead to widespread repeats... and people rediscovered it. Then, of course, its original copyright owners (Republic Pictures) used a complicated argument about other rights it owned to the story and music, to regain effective copyright of the picture, which it subsequently licensed exclusively to NBC. I do think that NBC is a good place for it (with a storied history and popular Christmas tree, etc.). Just wish they would show it more often.
As for TV, I like A Chorlie Brown Christmas. Nothing can top it, especially in its pure, simple message about the real meaning of Christmas.
I miss the old variety-show style Christmas specials put on each year by people like Bing Crosby, Bob Hope, and others. I would love to see Drew Carey or others do one again.