Thank you for the link. It was extremely interesting. This explains why my two favorite games on iOS (Canabalt and The Impossible Game) were never quite as popular as Angry Birds.
At its core, both The Impossible Game and Angry Birds are simple, but one is more successful to past to the next level. If you get one star on Angry By Birds, you can pass. On The Impossible game you have to have timing and be aware of what is coming up. I suspect this is the reason why the original Super Mario Bros. became so popular.