Last night I watched Santa Claus Is Comin' to Town with my kids. I don't know what is is about the old shows, but I think they are simply better than the new ones (even with the cheesy graphics and such). It's probably because these shows remind me of my childhood.
I still love The Year Without a Santa Claus (Snow Miser and Heat Miser seemed really scary when I was little, yet somehow they were still really cool).
I read in this morning's paper that A Charlie Brown Christmas turns 40 this year. So this show has literally been a part of every Christmas of my life.
Although it is much newer than the films listed above, Prancer has become a family favorite. It was filmed in my hometown (Three Oaks, MI), so it's fun to see the local landmarks. Even though I've seen in a dozen times, I still get verklempt when Sam Elliott reads "Yes, Virginia..." to his daughter.
But the perennial favorite is still Christmas Vacation.