Thinking about weelittledrummer's post, I can say that there is not really a song of anyone else's which I would like to have written. It is a bit like Shakespeare. I am just very glad we have it.
The songs I most wish I had written, are those which go through my head at sometime, but which I can't get down on paper before they slip away. They might not have have been classics, but I would have liked to have got them anyway!