I have enjoyed flight sim since FS95 through FSX. I finally made the move to Lockheed Martin Prepar3d v3 and have been very pleased. The addons that I use are Orbx FTX Global, Orbx FTX Vector, PMDG 737 NGX, PMDG 777, Fs2Crew, REX 4 Texture Direct w/Soft Clouds and Opus FSI. Although FSX has been a stable flight simulator platform, I am hesitant to believe that DoveTail Games will produce anything more than an arcade style flight simulator. It is my opinion that if you want a flight simulator with complicated systems and real life procedures, go with FSX, Prepar3d or X-Plane. I also hope that DoveTail will allow third party addons.
Lockheed Martin Prepar3d
http://www.prepar3d.com/
If you want to check out an open source flight simulator:
http://www.flightgear.org/
There also appears to be another flight simulator in development here:
http://nexgenflightsim.com/