White Christmas by Irving Berlin is the best selling single of all time and is studied on why it is popular for decades, and sold over 50 million copies. It seems to fall into the category of a likeable earworm.
Most songs follow a U-shaped curve of liking. New music isn’t liked very much, but as it gets familiar and is heard repetitively (on the radio and in the mall), one tends to like it more.
This repetition effect is U-shaped as too much exposure diminishes the fondness towards the song.