As a kid: Rudolph the Red Nosed Reindeer.
Teen years: A Christmas Carol (1951) with Alistair Sim as Scrooge. Used to show it on PBS channel each year, and our family (some already grown and moved out) would gather for dinner, then the movie. Special remembrances of my dad on these Christmas-y nights, as he's passed away.
As a Grown up: Miracle on 34th Street (original), It's a Wonderful Life, A Christmas Carol (1951), National Lampoon's Christmas Vacation. Special nod to Planes, Trains and Automobiles, which is great anytime from Thanksgiving to Christmas.