Looking for a Great iPhone Game

I have lots of cool ones - Orbital, Words with Friends, Frenzic, Ramp Champ… but I want something I can get involved in, not just a timewaster.

I had a Game Boy and Pokemon Silver back in the day when it was new enough and I was young enough that it was cool. I am of the opinion that it is still the greatest mobile game ever. Easy to play, lots of ways to make the game your own unique playing experience, and thanks to the trading system it was a ton of fun playing with others. It also didn’t require you to stay glued to the device - you could walk away if you had to, and on mobile devices that happens a lot.

Are there similar games - not so much in style, but gameplay - for the iPhone?