Onur Cobanli explains:
When you think of good design, you dream about how that good design will solve your problems; when you experience great design you are way past beyond problem solution point; with great design not only your problem is solved, you get a different, heightened level of emotional satisfaction and happiness; your dream comes true in this sense; while with good design you were simply thinking of getting rid of your problems, the desire was purely at functional need level; with great design your emotional desires are satisfied.