I would advise, as an industry, to pull back from this obsession with user wants and user needs and instead to design for fun. What you want your players to feel, what is the emotional path for them to get there, and how does your software—your business product, if that's what you're building—take them along the path?

Consider your own product. Is it fun, even without a goal? Does it indulge moments of playful exploration? Does it create moments of pleasant surprise? If so, congratulations because then you have a toy and you're on the way to building a great game.

As it turns out, there is no unifying theory of game design. To create games, we have to draw upon the art and science of psychology, mathematics, interaction design, and storytelling.