So many but these I can't miss. In no particular order:
Scrooged
Christmas Vacation
A Christmas Story
Fred Claus
A Christmas Carol: Patrick Stewart
Jingle All The Way
The Santa Clause
The Santa Clause 2
Miracle on 34th Street (young Natalie Wood)
It's A Wonderful Life
Elf
Toys (With Robin Williams. Not strictly a "Christmas" movie but has the feel of one. It's about a toy company and is really underrated. Plus the soundtrack is spectacular, with Hans Zimmer, Trevor Horn and many many others.)
S.J.