Words With Friends
This Scrabble-alike has taken the App Store by storm, and for good reason - it's incredibly simple to set up matches with friends asynchronously - i.e. you can compete but you don't have to be playing at the same time. This is by far the absolute best word game on the system. It's so easy to start playing and keep track of your matches that Words With Friends can easily suck up your free time. Buy it at the App Store.
Eliss
This is a game that could only be done with the iPhone's multi-touch input device. Designer Steph Thirion's planet-twisting game charges you with maintaining order in the solar system using only your fingers. And you'll have to use all of them - the game recognizes up to five simultaneous inputs, and you're going to have to multitask in an incredible way to squeeze, split, and shatter planets to get them to the black hole "squeezars." Buy it at the App Store.
Need For Speed: Shift
Easily the best arcade-style racing game on the iPhone, EA's flagship series adapts itself perfectly to the handheld, with fantastic controls, unlockable tracks and an RPG-esque driver experience system. While the multiplayer component is a little anemic, it's by far the most enjoyable single-player racer you can get. Buy it at the App Store.
