I use Real Flight G2 and love it. I think it was worth the money; I'm sure I would have spent much more money in crashes if I didn't use the sim.

With that said I think ANY sim that gives you a reasonable amount of realism and the ability to use your own transmitter or similar interface will be a benefit whether it is free or costs $200.

FMS is a free download for the software and you can use your own controller if you have a buddy box port. You will have to make or buy an interface cable however.

Here's the links:

FMS Software
Pre-made cable
How to build your own cable

Hope this helps,