The best are the old classic carols (pre-20th century) preferably done by a full concert-choir ... God Rest Ye Merry Gentlemen, Hark the Herald Angels Sing, Gloria/AngelsOn High, THe Wassail Song, too many to list. Not crazy about modern xmas songs or christmas rock (bad mix), especially detest 'Santa Baby'. Will someone tell me why I had to endure this 100x per season over past 5 years? Used to hear it once a year which was too much.
If I had to single one out to make sure i hear every year it would be "O Holy Night" by Tenn. Ernie Ford