On a 1080p TV, passive 3D is really only 540p since it has to render both eyes at the same time. So that may be why the quality didn’t look up to snuff. Active 3D can use all the pixels since it renders twice as many frames with the glasses blanking out every other frame for each eye. But active has disadvantages too because the glasses are expensive, heavier, require batteries, etc.
When 4K TVs become more prevalent, then it will be possible to have passive at 1080p and that might be a sweet spot. But for a while that will be an expensive option.
Specifically addressing your flight sim use case. I have played RealFlight
on my 27" computer monitor in 3D. I think I was playing v4.5 so it may have improved, but you can tell that 3D support was kind of an afterthought. The helicopters and planes looked good in 3D, but the environment did not look natural at all, so it was more of a distraction than a benefit and I switched back to playing it in 2D.
I am waiting for Oculus Rift
to be a little more mainstream and I think that will be the ultimate in 3D immersive gaming.