For more realistic flight simming, I recommend
FSX, and then depending on your taste:
if you like to push buttons and program sub-systems, the
PMDG-range of airplanes is best choice, namely the
737NGX. That one is a complexity monster, its simulated system depth is without rival.
If you are more after VFR or artistic flying, i always like the
SIAI Marchetti SF260 by Realair for that. Some reasonable WWII fighter addons are available, too, but of these I only know the Spitfire, also by Realair, also well-done.
An older package, originally for FS2004, but then converted to FSX, is the
Piper Cheyenne by Digital Aviation. In its class, this module is without competition. It'S excellent both visually and functionally. One sometimes can get it for reduced price these days.
If you want to do serious soaring, no way you can avoid
Condor then, an independent simulator, beefed up with some photo scenery addon.
Myself, I almost exclusively fly the 737-800 NGX these days. I only do turns with the bus simulator OMSI.
