The classic for me (childhood-wise) is A Christmas Story. TNT of course kind of bastardized it by running it continuosly for 24 hours on Christmas Day, but oh well.
I also like the stop-motion Rudolph the Red-Nosed Reindeer. It was also a childhood classic, but if you watch it as an adult you may pick up some interesting bits you missed as a child. For example... the sheer weirdness of the abominable snowman and his need for braces. Or the fact that Santa is a slavedriver to his elves, and is totally embittered and has no emotion at all. Favorite quote:
Elves: (cheerfully) Santa, we wrote you a song this Christmas!
Santa: (monotone) That's great. I'll be in my room. Santa exits quickly, and I can only imagine he disappears to drink away what little empathy he might have left.
Otherwise, Scrooged is pretty good, as is Trading Places. It seems that a lot of my favorites stem from the 80's, perhaps an indication of when my childhood and fondest memories of Christmas took place.