I fully support the FLIGHT DYNAMICS issue raised by Mathias above. I couldn't care less about people on beaches or inside (???) terminals.
We are talking about flight simulation, after all, not a social game.
My list of top requirements would include:
1) PHYSICS as realistic as possible (with the possibility of being tweaked by customers, in order to create custom variants or derivatives)
2) SCENERY as realistic as possible
3) WEATHER as realistic as possible (incl. Wind, Gusts, Clouds, Fog, Rain, Snow, Ice, etc)
4) PANELS (2D & 3D) and GAUGES as realistic as possible
5) RADIO NAVIGATION at least at the same level of FSX
Additionally, some FSX key features - like scenery and models - will hopefully be able to be imported.
GOOD LUCK, :ernae:
Ezio