How do you keep people from getting bored with your game?

From Donald Norman's Emotional Design: Why We Love (or Hate) Everyday Things:

First, the object must be rich and complex, one that gives rise to a never-ending interplay among the elements. Second, the viewer must be able to take the time to study, analyze, and consider such rich interplay; otherwise the scene becomes commonplace. If something is to give lifelong pleasure, two components are required: the skill of the designer in providing a powerful, rich experience, and the skill of the perceiver.

Of course, you can't control the perceiver. All you can do is try to design your game so that it encourages people to become the kind of perceiver who enjoys your game. For example, if you feel like beautiful sprawling landscapes are your strong point, don't create a racing game on a track. Your players won't even notice their surroundings as they zoom around. Instead, you could try having players race cross country to give them a chance to experience and appreciate the landscape.

I have two favorite card games that really fulfill Norman's concept of a lifelong design. Like most trick-taking games, Wizard gets much of its rich complexity from the other players. However, Wizard also adds two types of cards (a Jester that always loses and a Wizard that always wins) that makes accurate bidding more interesting.

Set, on the other hand, is just as enjoyable by yourself (as evidence by the Set Daily Puzzle). In this case, the richness of the game is provided by the ever-changing combinations of the funky designs on the cards. Even with the same layout, you can see many possible sets which extends your role as perceiver considerably.

Most video games today seem to be designed to be used and then tossed away. I'd love to see some more that try to be lifelong games.