I’ve found the perfect game for the iPhone or iTouch, its called Galcon and its a port of a game I enjoy playing on my Mac. Here is the link to it in the iTunes Store (you may need to upgrade your iPhone firmware to version 2.0 to support the new AppStore). It costs $10, but its well worth it IMHO.
Galcon is essentially a real-time version of Risk. You must battle with a computer-controlled player to capture planets using your ships. The more planets you capture, the more ships you can build. Playing the game is as simple as dragging your finger between planets to move your ships. You can control how many ships to move (as a percentage of those currently on the source planet) by tapping the % in the bottom-right of the screen.
The graphics are a little amateurish, but that doesn’t detract from the game’s overall enjoyability, in fact, I think the simplicity is an advantage. It gives the game an 80s feel.
I’ve always loved strategy games like Command and Conquer, and Galcon is this concept boiled down to its bare strategic essentials, with a UI that is perfect for the iPhone. Its actually easier to play on the iPhone than on my Mac!
Oh, and in case you are wondering, I don’t know Galcon’s author and have nothing to gain from plugging it other than encouraging its future development by putting a few bucks in its author’s pocket.