When I was a kid, it was the Albert Finney version of "Scrooge"
. I don't know why, but that came on TV every year in December, and we watched it every year.
Nowadays, I'd say the original "Rudolf the Rednosed Reindeer". I enjoy watching that with the kids.
EDIT: I prefer the "Mystery Science Theater 3000" episode of "Santa Claus Conquers the Martian".
And I want to watch the "Cinematic Titanic" version of "Santa Claus Conquers the Martians"