The Bishop's Wife (1947): With Cary Grant, David Niven, and Loretta Young. My favorite. I try to watch it every year.
A Christmas Story (1983): Based on Jean Shepherd's stories. The funniest Christmas movie.
A Christmas Carol (1938): The version with Reginald Owen as Scrooge.
As far as bad Christmas movies, I generally avoid movies I think will be bad, so I don't have any to mention, really.
Four! Make that four favorite Christmas movies. I forgot "White Christmas," which would be fourth (after "The Bishop's Wife," "A Christmas Story," and "A Christmas Carol").
Five! Add "Miracle on 34th Street" to the list, in fifth place.
(I should have read the other comments first.)