Grand Theft Auso: San Andreas has a very nice flight simulator aspect. It’s real world physics are realistic, but you don’t have to know about LORAN and ailerons and all that Flight Simulator crap—just jump in a fly away. It’s a blast because with some aircraft, you can bomb the hell out of the whole city and get the military after you. But you have to break into the airport and steal the airplane first :-p
At the start of the game, you have to go through the initial scenario of getting framed for murder by some corrupt cops and join your street gang homies and cause some general mayhem. But after that, the world is pretty much wide open to go and do whatever you want.
There are cheat codes to give yourself a Apache helicopter, make yourself invincible, etc.