I'm happy to call X-Wing a sim, and FS a sim. However, they're more precisely arcade sims.
I'd love to get I-War some time, though last time I tried getting things off GOG, the transaction simply refused to go through. But yes, truly realistic space sims are generally lacking. Orbiter is of interest to me, though I've not found the time to really learn the software. Space Combat can, like any sim, be "cheated" with in terms of reality and realism, but more so was incomplete and thus limited in scope. Most of the truly realistic sims out there are general sims (like X-Plane or MS Flight), and require a bit of imagination to hold your attention. Most of the time that works on my end, but sometimes one needs a bit more.
Of late, I've been playing with Starshatter. The physics are definately semi-realistic - they're better than FS's semi-newtonian physics, but they're certainly still not perfect. Until Infinity and the iNovae engine comes out, "true space sims" will probably be limited to old games most people don't bother to play with. Which is a shame.