Atari has released one recognized retro game on the iOS platform. It's Asteroids Gunner, and I can tell you it is very entertaining. And the great thing, is free and universal (runs native on iPhone/iPod Touch/iPad).
- 3 galaxies and 150 non-stop waves to test your rock-obliterating skills
- Three different ships to pilot: the Miner, Bomber and Dart
- Tons of power-ups and skill upgrades
- Unlock over 200 achievements to earn rank promotions and gain more upgrades
- OpenFeint and Game Center integration
You can find Asteroids Gunner from Atari in the App Store [iTunes Link].