Todd VanDerWerff writes about why A Charlie Brown Christmas continues to be one of the most popular TV specials ever done. He says it's because it quotes the Bible without being preachy. I think that's part of it. Affection for the characters in the Peanuts strip is another part. The music is yet another, and some of it is pretty funny.
Also, the show is refreshing and maybe a little closer to our own personal realities in that it's one of the few Christmas specials that isn't about a grouchy, Christmas-hating person who learns the meaning of Christmas and stops being grouchy. People — in this case, children — just start being more considerate of others…and it doesn't take visitations by three ghosts to make it happen. I like that.