The American Society of Composers, Authors and Publishers have listed the following as their top 25 Holiday Tunes (doesn't include very old traditional favs):

The Christmas Song (Chestnuts Roasting on an Open Fire)
Santa Claus is Coming to Town
Have Yourself a Merry Little Christmas
Winter Wonderland
White Christmas
Let It Snow!
Rudolph the Red-Nosed Reindeer
Jingle Bell Rock
I'll Be Home for Christmas
Little Drummer Boy
Sleigh Ride
It's the Most Wonderful Time of the Year
Silver Bells
Rocking Around the Christmas Tree
Feliz Navidad
Blue Christmas
Frosty the Snowman
A Holly Jolly Christmas
I Saw Mommy Kissing Santa Claus
Here Comes Santa Claus
It's Beginning to Look alot Like Christmas
Home for the Holidays
Carol of the Bells
Santa Baby
Wonderful Christmastime