A great songwriter is one who can say the most, in an entertaining and/or arresting way, in the shortest possible amount of time?? Discuss!

(not sure I'd absolutely always go along with the above myself, but it's one plausible working definition)

BTW, I've always had something of a soft spot for Mark Knopfler's extended guitar workouts, which is odd 'cos when it comes to other guitarists I can't stand 'em...