From Laminar Research:
X-Plane is the ultimate general-aviation flight sim with accurate controls and cockpit details. With hardware-accelerated texture-mapped graphics, dynamic speech synthesis, full-planet terrain-mapped scenery, helicopters, and the widest range of airplanes available in flight simulation, X-Plane will keep your eyes popping out for hours.
Being a converted Linux user now for over 3 years, the only thing that stopped me from a full Linux conversion was Microsoft Flight Simulator. With this product, the full Linux conversion is now complete and I love it! This product was better than I was led to believe!
Do not make this your first FS. You should know basic flight. More documentation would be nice. and the last con.. the PRICE!
Realistic as it gets for a PC. Gives the sense of true flight dynamics. User can design and fly their own aircraft designs. Aircraft design tools make it a breeze to create any aircraft you can imagine. Visually stunning if your PC has the horsepower. Even has a Mars sim for flying in another planetary environment. If you like MS Flight Sim X even a little, this is a must have. It gives you even more. It is easy to get started with, and allows the user to get as challenging as desired. Arcade levels to full true flight dynamics are available. Plenty of aircraft models from the programmers and other users available. They even hold design competitions for the best designs.
Not really a con, but huge load for the entire package. Eats up HD space when all areas are loaded, but what did you expect for having the planet in the database. Not to worry though, you can load selected land areas if your system is limited.