Although it's a newish film, I think that "Polar Epress" will become a classic must see christmas day film, we bought it for our kiRAB(age 5 & 4) and watched it last week on dvd, it was brilliant, we'll probably watch it again on Christmas Day & then not bother with it again until next Christmas!! But it is a beautifull film for little kiRAB.
For adults & kiRAB, I think that the Home alone films(1&2 only) are just great.
Miracle on 34th street was a sweet film aswel.