The primary problem with space sims is creating the universe. Space is so... inherently foreign to us that the first... and conceptually most difficult problem, is "divining the universe." If you can't craft a good story, the game will flop no matter how fantastic the engine is. The next problem is the engine.
FS is great because it has a coherent universe with a coherent engine. The engine is coherent because your operational environment is restricted (no planets or gravity to deal with), and thus everything obeys the laws of the environment as defined by the code. This, in its own way, makes the FS universe realistic.
A potential problem... and I'd assume accurate for many games/sims today... is that in attempt to increase the "range" of the universe, the complexity of the code augments.
Well, that's obvious... The problem is trying to simulate everything... without devoting the necessary computing power/coding to make it happen. Half-way realistic or half-way arcade isn't
anything. You can't have both. You can make realistic easy and arcade hard, but you can't mash the two together. That is really the death knell to an engine in terms of user emersion, as it
breaks the laws of the over-all environment; it breaks coherency.
So, until your developers... or you have the initiative... to forge a "soulful," spirited universe which feels real in terms of the story,
and design an engine which doesn't make any glaring compromises to itself such that it becomes compromised, you're not going to see the next great space sim.
FS is the best, hands down, because it hit both problems right on the head. And think about it,
every great space sim follows the said model of good story, good engine. No exceptions.

By the way, I'm glad to see you're still around, Badman.
