Without a doubt, A Charlie Brown Christmas is my favorite Christmas TV special, though it's difficult for me to explain exactly why.
A lot of it definitely comes from the jazzy soundtrack by the Vince Guaraldi Trio. I know many people criticize it as being too sad and melancholy, but that's one of the things I love about it, and in fact, the special on the whole. It's one of the few Christmas movies/specials that acknowledges the bittersweetness that goes hand in hand with all the holiday cheer. For many, Christmas can be a reminder of what they're missing, of loved ones gone or traditions soured. Even the Christmas cheeriest of us can feel twinges of sadness throughout the season as we anticipate it's demise. And no matter how swimmingly your holiday goes, there will always be a letdown after the big day has passed and all the planning and preparations have come to fruition.
It's certainly appropriate that Charlie Brown, the hard luckiest of heroes, is the star of the most melancholy Christmas special, but the show isn't all doom and gloom. It is about, like the Community episode it, in part, inspired, the search for the true meaning of Christmas. While the story seems to settle on a decidedly Christian answer to that question via Linus' recitation of bible scripture detailing the birth of Christ, for me, A Charlie Brown Christmas has always come to almost the same conclusion that "Abed's Uncontrollable Christmas" does: that the meaning of Christmas is that Christmas has meaning, and that meaning can be found most anywhere, whether in the bible, or the prize winning decorations of a dog house, or the gathering of friends, or a sickly Christmas tree, or Charlie Brown's restored faith in the holiday.