One of the reasons I believe games are such an effective tool for marketing (and communication) purposes is that it grabs us in a magical way that commercials and adds can't (anymore). This video illustrates how many adds and commercials we see every day, but which brands actually stick? The ones that go straight into your heart? The ones that are funny? Relevant?
I strongly believe that relations are build through interaction. The more compelling and dynamic the relationship is, the more intense it will become. Compare this to the relationship with your best friend, husband or girlfriend. The reason why your relationship is so special is because you've come a long way. You have crossed many rivers together from mountains high to valleys low... This is the same experience a game gives you when playing it. A good game* will invite you, seduce you and challenge you level after level. This is why people become so passionate when talking about classic games... check it for yourself next time you see your friends. Start a discussion about classic games like Donkey Kong, Mortal Combat, Tetris, Sonic or Mario... you'll see!
* This is actually the theory of flow. If you want to learn more about the theory of Flow check this search box above and enter 'Flow'.