There is a good summary post at this forum regarding the available R/C sims and interface vendors.

As Wright Flyer mentioned, just make sure that you get a TX-to-gameport or TX-to-USB interface, which will make your transmitter visisble to all Windows applications as another joystick.

There's an on-line manual on configuring such an interface to work with many freeware and commercial simms:
http://www.milehighwings.com/gameport_guide/index.htm

Have fun!