The Flightgear flight simulator was not created by a single person. It was created by international group of volunteers. It is open source software free to download.
FlightGear Flight Simulator was by the FlightGear Project since 1997 and was the first FlightGear released.
Some free flight simulators include YSFlight, FlightGear, and or Orbiter. Google those names for more information and/or to download. Also, Google Earth comes with a free flight simulator.
Flightgear is an open source flight simulator you can download. Likewise, Google Earth provides a free flight simulator with choice of two aircraft: F-16 and SR22. The only good online in-browser flight sim I have seen so far is a google earth-based flight simulator that uses the google earth plugin. See related links below.
Microsoft Flight Simulator was created in 1982.
Free flight simulators can be downloaded on line at various websites such as softonic, flightgear and gefs-online. These simulators will be pretty basic.
Echelon - flight simulator - was created in 2001-03.
The most popular flight simulator is called Flightgear. It is open source and downloadable from: the flightgear website. The latest version is 2.1.0 and there are many additonal planes and the entire world map to download for free. You may also buy the game CDs where money goes to charity.
Actually, there's a program out there that's very very similar called FlightGear. Some may say proflight actually stole flightgear. Anyway, FG is totally free, check it out.
Microsoft Flight Simulator X was created on 2006-10-10.
FlightGear was created on 1997-07-17.
Combat Flight Simulator WWII Europe Series was created in 1998.
You could try YS Flight Simulator. It's got a good community and seems to be in development. Although don't expect good graphics from it.