God is the difference between a good and great U2 song

On page 177-178 of Bono, the U2 singer is asked by Michka Assayas where his best ideas come from:

Michka Assayas: 'I don't know how it is for you, but my best ideas come when I'm about to go to sleep, or when I feel like I have spent my entire day wasting time, or working without thinking, which may amount to the same thing. I go down to buy a paper, and all of a sudden the idea that I was looking for just happens.'

Bono: 'Yeah, the unconscious. Whether it's a collective unconscious or not, whatever pool you draw out from. That's why songwriting by accident is so important, and the getting to the place where that can happen or, as we say, getting to the place where God can walk through the room. Because, if you know what great is, you know you're a long way from it.'

It's not always easy to tell the great U2 songs from the clunkers, but to me, "Bullet the Blue Sky" is one of the great ones, while a handful of the songs on Pop aren't the greatest.