Versions: V1 (also works for V2)
Yes. The G2/G3 is a USB game controller and FS One can read any generic USB game controller.
Plug in the FS One interface (V1 or V2 interface) and connect a transmitter to it. Plug in the G2/G3 controller. After both controllers are plugged in, start FS One. Then select the interface from the fly page (e.g., Single-Player Freestyle) by clicking on the “Select Interface” button. Then click on the Transmitter icon, and pick the Tx category called “Other RC Controllers”. To calibrate, click on “Calibrate” and follow the instructions. When flying, use the spacebar-key to reset and the u-key for instant up.
When picking a new aircraft, be sure to also pick the appropriate Tx from the “Other RC Controllers” Tx category on the Transmitter Selection window. In other words, to fly the Hangar 9 Edge 540 33%, pick that Tx in the “Other RC Controllers”.