I believe it was someone on the ocolus team (carmack maybe) who mentioned what I call the horizon test: does the horizon (appear to) remain level when you tilt your head doelwn to your shoulder?

It's a pretty demanding latency test, and I can also see how it ties into balance etc (there are some similarities with a tilting boat deck, for example).

That said, I think simulator sickness and sickness from just playing on a big screen is complicated - maybe some will never enjoy it.

Personally I'm rather sensitive to motion sickness from most fps games - but I enjoy playing elite:dangerous with a vr headset.