First is Scrooge (1970). It's usually the first movie I get around to when December hits, and I still feel rather warm and fuzzy when the titles begin and I remember my first glimpse of the movie, back when I was a wee lad of five or six. Read the review here: Scrooge (1970): Film Review. I also penned a related piece, Who Was the Best Scrooge?, in which I review a handful of different actors in the role, including Alastair Sim (of course), Michael Hordern and Seymour Hicks. And lovers of linguistic trivia may find this article interesting: What Does 'Bah, Humbug!' Mean?
The second seasonal film is Gremlins (1984), which has a fun mix of holiday nostalgia, dark comedy and monster mayhem. Read the review here: Gremlins (1984): Movie Review.