I can give you a list of favourite songs. I can have a look on my last.fm page or my itunes library and see what I've played more often than others, but of all the songs I know, to try and pick out one that stands discernably above any of the others is impossible.

As for your assertion that your favourite would have changed by tonight, can i just say that *that's* quite impressive. Mind would have changed by lunchtime!

And I'll brook no argument on the subject.

By Throbbing Gristle. Anything else would be madness.
Or,Penny Lane?

… it's this.

I don't know about it being my favourite song, but this is definitely up there among my favourite records:

but it's a secret, I'm not telling you what it is.

Oh... ok, then... it's God Only Knows by The Beach Boys.

Greatest song ever written.

and the rest of this thread, my friends, is mere conversation.

by media whoring but "Another Girl, Another Planet" is currently sitting in that spot (but give me 15 minutes).

I'm with GaryT on this. I think many of those already listed are great performances of songs, particularly Dylan's 'Like a Rolling Stone', but for it to be a great song there has to be a number of other great performances of it in different styles.

So, my nominations for the greatest song would have to include Folk Songs which have survived loads of interpretations over the centuries and some from the 'Great American Songbook' which can be performed in all sorts of ways and still survive intact. Having considered a number of Cole Porter's and others, I think I will have to go for 'Summertime' by the Gershwins. You can have every interpretation from Opera, through easy listening to full-on Jazz and Pop, but when you hear those three notes you just have to sing 'Summertime and the living is easy'. It's a great song because it is great to sing.

Child of Vision by Supertramp....no idea why (perhaps it was because I was looking at my 5 month old daughters toys?)

A great song but not the best ever.

or it could be something else.

Dark End of the Street.
James Carr.

I win.

...The answer will always be 'Footloose' by Kenny Loggins.

about best song, but best record is I think Dancing Queen. Much as I love the Beatles, I don't think even they came up with as many hooks on one track as this. Just perfect production too.

...is absolutely one of the greatest songs ever written or performed. Jerome Kern wrote a lot of nice songs, but that one wins. Ole Man River is also a great song of his.