If he hadn't written 'Yesterday" "Wonderful Christmastime" would be an unpardonable crime.
It is weak, words sound like something a toddler makes up, and the tune is insanely basic and dull...and then there is the production, with the casio keyboard.
Had ANYONE ELSE written this song, it would never have gotten airplay, and would be forgotten. I suppose he wrote this very quickly after seeing how popular John's Christmas song was...and there is absolutely no comparing the two, "Happy Christmas" is a true classic...even Yoko's catterwalling on it doesn't kill it.