I should mention some good ones, too. I love “Santa Claus is Coming to Town” performed by the Crystals on “A Christmas Gift for You from Phil Spector.” You can have a listen to a bit of it here.
I’m also quite fond of “God Rest Ye Merry Gentlemen/We Three Kings” by Barenaked Ladies and Sarah McLachlan. Give a listen here.
All of them are rubbish (particularly if you work in retail - my heart goes out to you), especially the one that goes (and is probably titled) “It’s beginning to look a lot like Christmas…” That’s because it’s Christmas, you moron.
Oh, and Santa Baby just sounds plain wrong.
The only exception is Fairytale of New York, because it’s impossible to hate a song that contains the lines:
You scumbag, you maggot
You cheap lousy faggot
Happy Christmas your arse
I pray God it’s our last.
That’s the spirit!
I’m late to the game, but for best I vote for Someday at Christmas by Stevie Wonder.
As for worst, I’m tempted to say it’s I Want a Hippopotamus for Christmas for its parasitic way of eating into your brain, but there can be no worse song than The Christmas Shoes.
My all time favorite Christmas track is Rowlf the Dog and John Denver doing Have Yourself A Merry Little Christmas.
Oooh, I’ve never actually seen it, but it’s on Youtube.
Surf rock has produced a few good interpretations of Xmas songs, notably
Dance of the Sugar Plum Fairies - Rudy and the Surf Kings (they have an entire Xmas album, but this one is the best).
Gin Com Bells - Estrumental
The Saracen Gift - Pollo del Mar (I loathe the traditional rendering of this song (The Little Drummer Boy), but the Pollo version sneaks up on you with strange minor harmonies before you realize what it is they’re playing).
And of course, no Xmas song gets me in the mood better than Spinal Tap’s “Christmas With The Devil”.
As to the worst, I don’t have the courage to listen to this one, but Mrs. J. (a collector of Xmas music) reports that Frankie Valli and the Four Seasons do a version of I Saw Mommy Kissing Santa Claus that would make even the cheeriest person contemplate defenestration.
Thank you. I just heard “Grandma’s Been Run Over By a Reindeer.” I had actually managed to forget that mostrosity! Makes one long for the good old days when our store played musak.
I’ve never heard “Christmas Shoes” & I don’t want to. If its worse than the above & “Feliz Navidad”, it must be a pip! 
I gues I’m the only one who enjoys Grandma getting runover once or twice a year.
My favorites:
Pretty Paper (because blue ribbons remind me of Hanukah)
We Need a Little Christmas
Worst:
No competition-that horrible porky pig Blue Christmas-I can’t stand more than 3 seconds of it!
Worst lyrics:
The Cat Carol linked above is my new most hated lyric ever.
I have finally heard it. Ok, imagine this:
You eat 4 servings of cotton candy, so you’re full of sugar, and sticky. You then go on the “tilt-a-whirl”. Sickly sweet. And, it makes no sense, so it made my head hurt- why does Jesus care what shoes the kid’s now dead Mom wears?
You’ll find one here that you might like (that’s an authorized download). If you want to hear it before downloading, it’s the 9th song on this page.
You’re welcome! 
For best, I must nominate The Little Drummer Boy, a crappy instrumental version of which reduced me to tears yesterday while I waited in the freezing cold at Newark Penn Station. It’s crazy when you don’t even have to hear a good version of the song to be moved by it.
Dude, what’s pretentious? It’s about a kid who’s too poor to bring anything fancy, so he gives the only thing he can–his music. Damn it I’m going to cry now.
For worst, I’m going with anything sung in an obnoxious little kid voice, like that ‘‘I Want a Hippopotamus for Christmas’’ song. I’ve got nothing against Hoppopotamuses, mind you–just the obnoxious children who sing about them.
Let’s take a moment and remember the phenomenal singer who gave those words such resonance, the late, great Kirsty MacColl.
I miss her terribly, but I’m so thankful that she’ll never be totally forgotten if only because of that song. Many many millions of people have heard her voice who have no idea who she is, but they remember those words. She would find that quite amusing.
Agreed. She was absolutely phenominal. I heard a cover of Fairytale in a department store the other day and was reminded, by listening to someone do an inadequite job of her part, just how special her voice was.
I’m sorry, there are some songs that should never be covered. That’s one of them. I’m appalled that such a thing exists.
Amen to that, Equipoise.
Best: Elvis Presley singing* Blue Christmas*, a wonderful wonderful song that is also sung movingly and amazingly by Rita McNeil. “Silver Bells” by the aforementioned Ms. McNeil. Elvis Presley’s version of* Santa Claus is Back in Town*. There ain’t nothing better and if Elvis had never sung anything else but that and That’s All Right, Mama, he would still be immortal. Loreena McKennit singing Good King Wenceslas and/or God rest ye merry, gentlemen.
Worst: David Bowie and Bing Crosby doing something unmentionable together that was, somehow and in some hellish way, released as a recording of that vile excrescence on the music scene known as The Little Drummer Boy. There are duets and then there are monstrous pairings, and I know which that was.
Feliz Navidad, while icky, is not on the same plane, ickwise, as Bowie/Crosby.
Fun once a year: Little Miss Dynamite (Brenda Lee) and Rockin’ Around the Christmas Tree.
Lovely with the right singer: O, Holy Night. What Child is this? The Coventry Carol.
Horrid: The Cat Carol. But you know what? Much as I hate it, and I DO hate it, it still causes tears to stream down my withered cheek.
I have never heard The Christmas Shoes, for which I daresay I am thankful.
Good LORD, that was FAITH HILL??? I heard that the other night for the first (and please G-d I hope the last) time and was utterly appalled. It’s horrid! Terrible tune, stupid repetitive lyrics. Everything about it just plain sucks donkey balls. Having never heard the Christmas Shoes one, this was the song I was going to nominate, but since you’ve already done that, I’ll just second it. Ugh.
Thanks so much for posting that link. I’d almost forgotten what a beautiful voice John Denver had.
I like so many of the classics, but my new favorite Christmas song (yes, I’m Jewish and love Christmas music, so sue me ;)) is Mary Did You Know by Kenny Rogers and Wynonna Judd. It’s almost hauntingly beautiful. This is the live version, which obviously isn’t as perfectly mixed as in the studio recording, but sometimes it’s nice to see performers actually perform their songs, so I submit this for your viewing as well as listening pleasure. 
Merry Christmas everyone!
Oh, and I love Santa Baby! 
Best
"Silent Night" - it’s the quintessential Christmas song - beautiful, simple, and humble. Just a piano accompaniment.
Honorable Mentions -
****“O Holy Night.” ****I love the rendition my Simon Cowell’s group Il Divo, even though I kind of hate them. But I love the energy and range they bring to the song. I also think Mariah Carey nearly nailed the song until she started in on her vocal acrobatics, which ruined what would be a great song.
"O Come, O Come Emmanuel" by Mannheim Steamroller - done in Latin with a gregorian chant flavor. Beautiful
"Greensleeves" - I like one of Mantovani’s arrangements best but I haven’t heard an orchestral arrangement I didn’t like.
Worst -
"Christmas Shoes"? Awful on every level imaginable.
Dishonorable Mentions:
Stevie Nicks’ “Silent Night” - her butchering of this classic song is criminal
I love Bowie & Bing’s duet of “The Little Drummer Boy/Peace on Earth” in a wholly un-ironic manner. It’s the duet that should have been from hell, but came instead from heaven. Deeply wrong and laughably stupid gone beautifully right, and thus, amazing on more than one level.
“O Holy Night” is a song that seems to lean quite heavily on the singer’s voice. That sounds a little ridiculous, but you know what I mean. Style, character and practice won’t get you by, as it might on others. You must have a gifted voice for this song, or you’ll end up with ‘meh’ at best.
“A Charlie Brown Christmas” is my all-time favorite Christmas special, and Vince Guaraldi’s music from same is the CD I can’t tire of.
**WORST: **I can’t believe nobody’s mentioned “I Farted on Santa’s Lap.” A true Christmas classic. I’m so glad I haven’t heard it this year.
I’ve never heard the Christmas shoes song. I’m just lucky, I guess.
I love “Adeste Fideles” by Nat King Cole. Actually any Xmas song by Nat King Cole is awesome.