FlightGear has the most realistic flight dynamics engine and weather simulation. Great graphics - turn up settings from rendering and 'detailed weather' menus first. Openstreet map based cities are downloadable. Terrain for whole world downloaded as you fly. Lots of aircraft with detailed systems: c172p/c182/J3-Cub/PA-28, A320/MD-11 , F-14/Saab Viggen/F-15/F-16 , Space Shuttle, DHC-6, EC130 and lots more - filter craft by quality. 700 aircraft are super easy to install with 1 click from launcher, but there's a fair amount more that can be downloaded from github or 3rd party hangars.