Scott,
I wish I knew why some musically simple tunes are hits and some of the good ones aren't.
I used to have this discussion with my dad who was a professional sax player until the day he died. When the Beatles came out he thought their music wasn't very good. I sat him down and we listened to some of their good tunes like "Something" and "Here There and Everywhere". I said to him "dad are Alley Cat and Cab Driver really better tunes musically than these?" He had to agree that they really were simple nothing songs. Yet they were popular.
That being said here are the reasons that I've come up with:
Good beat for dancing - "Alley Cat", "Elvira", "Stayin Alive".
Cute catchy lyrics - "Rolling on the River", "She Loves You Yeah Yeah Yeah".
A melody that you can walk away humming -"Your Cheatin Heart"
A cute story - "Leroy Brown"
A socially timely tune - Any 60's anti war, love one another, peace type song I can't remember the titles but the lyrics for this type of tune go "Somethings happening here, Stop children what's that sound, and " Go ahead and hate your neighbor go ahead and cheat a friend'.
Popular love songs when you fell in love -"Never My Love", "At Last" and similar type songs.
Songs related to a specific event - "Edmond Fitzgerald"
Patriotic tunes - "God Bless the USA", "Ballad of the Green Berets"
Finally there ARE good tunes that are done well that do become popular - "Rainy Days and Mondays", "After the Loving" and "Inna Godda Da Vida".
Tom