Well, "Tie a Yellow Ribbon", just like "Sally Gardens" and a lot of Child ballads, was generated by the pressures of its time. So was "Yankee Doodle", which I am sure sounded like Johnny-Come-Lately lyrics at the time, but surely counts now as a well-beloved folk song.

"East Side, West Side" was a TinPan Alley commercial sockdologer in its time, but is notalgically hummed by old folks today and might qualify.

So I submit that it is not the pop-ness of a song, but the depth of its roots in the sentiment of those who know it, that makes the difference. The harsh and chaotic songs of our youth or of today's, provided by the Stones or the rappers, will go by the wayside, while those which actually capture the feelings of the time (Michelle, If I gave my Love to You, Masters of War, God on Our Side, the Canadian Railtoad Trilogy...countless pieces) will survive. If time alone is the test, they will probably pass it.