"It's all about the surprise effect"
I'm often surprised by how emotionally I react to certain moments in Mark's songs when I hear them for the first time. That can be a chord change, a lick, the combination of meaning and music ... anything. He regularly comes up with such moments, so I'm no longer surprised that they come, but I always am when they do.
I'm not so sure (as Sting is) whether an element of surprise is a necessary ingredient for a good song, though. After all, any surprise will be gone when you listen to it the second time. A great song stays great, however - even when you know it by heart and there are zero surprises anymore.
When it comes to judging the quality of songs, I follow this simple rule: The more I want to listen to the song again, the better it is. I'll want to listen to "Watch Me Gone" a great many times.