It's a Wonderful Life. This one has real staying power, if nothing else. It's also sentimental enough for Christmas without being overly manipulative. It's a great story, the family and friends theme is both Christmas appropriate and timeless. It also has the interesting characteristic of an historical relic, with its strains of progressive (almost socialistic at times) politics.
Merry Christmas, Charlie Brown. This one is really more a TV special than a movie, but I think it has transcended its original context. Great music. The pacing is nicely done, moving back and forth at just the right speed between Snoopy's antics and the kids' story. Extra points for being the only one to quote the entire Christmas story from Luke. Linus is my hero.
Elf. The best recent one without question. Will Ferrel can be be tiresome in the wrong role, but this one suits him. Also, this one has the best Santa Claus---a cantankerous old connoisseur of NYC pizza. Extra points for making fun of the puppet movies. Best line: "Don't listen to Leon, he's never been anywhere; he doesn't even have feet!" Runner-up: "Bye, Mr. Narwhal."
A Muppet Christmas Carol. Christmas Carol adaptations could really be a separate category. Really, the only way to see it is on the stage. On screen, this one is my favorite.
Home Alone. Great characters. Physical comedy. A great soundtrack. An old man beating robbers with a shovel. What's not to like?
Scrooged. I like this overlooked Bill Murray performance. It doesn't have the festive-ness or the fun of the muppets, but it stays true enough to the story to be recognizable and plausible, while at the same time varying from it enough to avoid being nothing more than a remake of the George C. Scott version.
The Snowman. I'm not crazy about the altar-boy vocals during the flying scene. But telling the entire story sans words and keeping it engaging takes skill.
How the Grinch Stole Christmas. No, I'm not talking about that abomination with Jim Carey. The original is a classic. Who would have thought Boris Karloff would star in a Christmas film?
All the stop-animation puppet films. Okay, I know these are pretty much a holiday staple. But they're so overrated. If you sit down and watch them without the nostalgia, you realize they're really not all that good. One exception: The Year Without a Santa Clause gets extra points for the heat miser and cold miser routines, and Yukon Cornelius is the best character this genre ever produced. Also, extra points for having a yeti as a main character.
The Christmas Story. Another staple, but I'm going iconoclast with this. Maybe this movie isn't completely no good, but it is hugely overrated. It's so deep in nostalgia that it can't even see the plot. It has some funny moments, no doubt. But it certainly doesn't deserve the 24-hour Christmas Eve marathon it sometimes gets. Minus extra points for inspiring The Wonder Years.
Santa Claus: The Movie. This is a 1985 gem starring Dudley Moore, the 80s' favorite low-budget excuse for Paul McCartney. It gets points for doing a pretty decent job with explaining the origins of Santa and for doing a' decent visualization of the North Pole. It loses points for starring John Lithgow and having a very dated sound to the music.
Any sequel to any Christmas movie. Due to the electromagnetic force generated by the earth's rotation and tilt, the law of sequels (explained here) is several magnitudes stronger around the winter solstice.
Just Plain Ugly:
George and the Christmas Star. In this heartwarming animated tale, the title character decides his tree needs a start and decides to go on a space journey to get one. This is the worst Christmas movie ever produced. And probably rivals "Plan 9 from Outer Space" for the title of worst movie ever. Minus 10 for using Paul Anka to write the music.