When comparing Freedoom vs FlightGear, the Slant community recommends FlightGear for most people. In the question“What are the best open-source games?” FlightGear is ranked 4th while Freedoom is ranked 38th. The most important reason people chose FlightGear is:
FlightGear has scenery that contains environments to fly in from the whole globe.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro The Doom feeling without the proprietary data files
Pro Thousands of available mods
Pro Easy mod creation
Making new levels and even gameplay mods is fairly easy and requires no programming knowledge.
Pro Easily moddable
You can apply mods others have made in a straightforward fashion. Find a mod you like (either from a quick google search or checking moddb for some) and the individual mod pages have a "tutorials" tab that you can use to figure out how to install it. It differs from mod to mod, but in most cases, it's fairly simple.
Pro Well documented modding possiblities
There are numerous tutorials providing detailed help with the modding and wikis providing extensive information on all aspects of the game
Pro Active community
Pro Worldwide scenery
FlightGear has scenery that contains environments to fly in from the whole globe.
Pro Free and Open Source
All code written for FlightGear is opensource and available for anyone to use.
Pro Crash animations in some aircrafts
Pro It has world-wide multiplayer
Pro Live cockpit
Pro A lot of aircrafts to add
Pro It has amazing graphics
Pro You can almost recreate real incidents
Pro No bugs
Cons
Con Not as graphically advanced as commercial competition
Con Getting stuck upside down
After a crash a pilot may be stuck in an upside down position with no way to recover.