Since you said realistic flight, and if your wanting to play around with 3D than the only sim you need is Aerofly Pro. I've got G2 also and Aero-fly Pro wins hands down.
Aerofly doesn't have all the cute and pretty planes but they fly like a real one and if you want to learn 3D it's not going to happen with G2.
If all you have is usb then you'll need an adapter for the 15 pin connector with areo-fly.

Here's a good place to read about it and see a couple of video's.
http://www.joeycomputers.com/board/viewtopic.php?t=479