Tough to pick just one

The original Scrooge .
The Scrooge with George C Scott is another good one
The original Grinch is another top one for me
White Christmas is one of the best ones ever made. With an all star cast beyond compare.

I also like the original Claymation shows , such as the little drummer boy etc etc

For Modern movies.

Elf
And Christmas with the Cranks are up there.