I worked at a museum with a planetarium. The way it was explained to me was that if the stars move — as far as your brain's visual processing is concerned — you must be moving. After all, the stars are fixed points of light; they never move unless you are yourself spinning in some manner — except, of course, in a planetarium.
We also had a flight simulator; but with that, the movements of your body mostly matched the movement of the plane (you couldn't feel forward/backward acceleration, i.e., acceleration on an axis perpendicular to your chest, as otherwise, you'd be actually moving around in the building). This never made anyone sick. The planetarium, however, regularly made people feel ill, and occasionally I'm told, actually lost their lunch, whereas nobody ever lost their lunch in the flight sim AFAIK.
We also had a flight simulator; but with that, the movements of your body mostly matched the movement of the plane (you couldn't feel forward/backward acceleration, i.e., acceleration on an axis perpendicular to your chest, as otherwise, you'd be actually moving around in the building). This never made anyone sick. The planetarium, however, regularly made people feel ill, and occasionally I'm told, actually lost their lunch, whereas nobody ever lost their lunch in the flight sim AFAIK.