I love It's a Wonderful Life, but I do find it somewhat ironic that it wasn't supposed to be a Christmas movie.  That it revolves around the holiday is just a case of the consumers knowing more about what the movie means than perhaps the director did.  I don't watch it as much as I used to, having gotten it on video tape, and later on DVD.  I guess the convenience of seeing it when I wanted, rather than having it available as one of the limited choices I had airing on the small number of broadcast channels we got on the TV when I was younger.

I guess for me the movie that works best as a Christmas movie is the original Miracle on 34th Street.  It's silly, but I believe.  I love that movie too, and would have a hard time choosing between it and It's a Wonderful Life, but knowing that Miracle on 34th Street is all about Chris Kringle, I have to give the edge to it.

Finally, the other movie/TV show that ranks up there is the original How the Grinch Stole Christmas.  You are a mean one Mr. Grinch.  I love the animation, Boris Karlof's singing and naration, the whole kit and kaboodle.  Definitely a classic.