I am satisfied with iPhone 3gs gaming features. It had improved performance and better 3D graphics. Apple claims that iPhone 3GS will be 2x times faster than iPhone 3g and it is true.
Maybe I've just not tried the right games but I'm dissapointed by the gaming. I mean sure there are some wacky things you can do with touch screen and sensor controlled games - but without a physical D pad the experience will never be that great for gaming for me. Though that being said I still use it a lot for gaming, things like warfare inc. are really fun.