Try X-Plane 9. An amazing flight simulator, controlled using the accelerometers by tilting the iPhone. It has a 172, Columbia 400, Cirrus Vision and Piaggio Avanti.
There is a visual mode and a very realistic instrument mode, but to be honest, it is way too sensitive to fly on instruments and there is no autopilot. However, the visual mode is great fun, particularly in the Vision, blasting around the Austrian Alps near Innsbruck at 400 kts at low level.
There are new airliner and helicopter apps which I haven't tried yet.