I find it interesting that the question is asked about a “favorite song,” and everyone responds not just with song titles, but the artist who sings them.
There was a time when it didn’t matter who performed the song, but the song stood on its own. Of course, there are classic performances of a song, but if a song is a classic, most anyone should be able to record it, and interpret it.
For me, when I think of “favorite song,” I think of things that have endured because the songs themselves are works of art, great poems or wonderfully crafted lyrics combined with a beautiful melody and harmonic flow.
There are sacred standards that have endured: Amazing Grace, How Great Thou Art, and some enduring sacred choruses that are simple, yet convey an eternal message.
There are classic standards of the american musical theater and jazz that have endured: some of my favorites include “My Heart Stood Still,” “All the Things You Are,” “My Romance,” etc.
A “song” should be something that I can perform and interpret myself. It should be more than a vicarious experience. And, IMHO, it should stand on its own, without concern about who performs it.
“Its fiction, but all the facts are true!”