I will agree that the Mannheim Steamroller stuff has not dated well. I do like some of it but quite a bit just turns my stomach these days.
It's not really the Christmas season for me until I have given at least one spin to Herb Alpert & the Tijuana Brass's Christmas Album, which contains the only version of "My Favorite Things" ever playing (unless you are watching The Sound of Music) and a great song called "The Bell that Couldn't Jingle" that would have made a good seasonal TV special.
And, I always need to hear the Leroy Anderson arrangement of "Sleigh Ride" a few times a year. My favorite version is Arthur Fiedler and the Boston Pops.
The newest Christmas song I like is "Best Christmas" by Christopher Cross.