It would be utterly impossible for me to select a single song as my favourite of all time. However, I find it hard to disagree with the late, great John Peel (a British DJ of legend to my generation) who reckoned that The Undertones' Teenage Kicks was the finest single pop record ever made.
I love most kinds of music, have many many favorites, but if I had to pick only one it'd be Dylan's "Changing of the Guards." Can't find it on YouTube, though- his original has been deleted, and all there are are covers.
Yes and he's done something weird with his teeth so he talks as though he's slurring now....but he was GORGEOUS in his heyday