Your ONE all time favorite love song?

I've actually didn't pay attention to the OP's request for LOVE song(perhaps due to the assumption that best songs are about LOVE), but nevertheless, I get stalled when hear Sade's Haunt Me.

Wow this thread has been alive for along time, since before the creation of Youtube. I digress...

Operatic love song goes to Una furtiva lagrima, from Donazetti's opera L'Elisir d'Amore. The elixir of love. Here is Ramon Vargas singing it with subtitles.

http://m.youtube.com/watch?v=_qvhEkOkGgg

YouTube cannot do it justice, but you get the idea...

"Here and Now" Luther Vandross. And of course "In my Life" and "Glory of Love".

"Heard It In A Love Song" Marshall Tucker Band

Black Coffee with Ella Fitzgerald is good.
link; https://www.youtube.com/watch?v=NjOoD94ucEQ

Or Frank Sinatra; Angel Eyes; https://www.youtube.com/watch?v=AJ04Lwt2PlU