It all depends on the money. FMS is useless, HeliSimRC is a bit better, but still bad, and free...
ClearView is a good sim if you don't have a lot of money.
Aeroflight should be pretty good, but I never tried it myself.
What do you want to fly, planes or heli's?
The 2 best sims you can get are Phoenix and Realflight.
Phoenix is a very good heli sim, and Realflight is a very good plane sim.... (but they are both expensive)