Sometimes the simplest games and concepts are the most popular. I think that's the case with Angry Birds. It's a very simple game - even a 5 year old could play it. But yet the simplicity makes it huge. It's also endless. So once you're hooked, you have more and more to look forward to. Take notes if you plan to be an inventor someday. The best products are:
1. simple (anyone can enjoy it)
2. inexpensive (the game downloads are cheaper than a value meal)
3. continuous (customers feel impelled to go to the next level or buy merchandise)