Some FPS games make the mistake of limiting field of view, which can cause motion sickness on regular monitors. A wide field of view and high frame rate greatly improves things.
With VR, it's a combination of frame rate and as the comment above mentions - too much movement. In No Limits 2 rollercoaster for example, you can walk around the park and get on the coaster, ride the coaster, then get off and walk around again - it's too much. The best VR I saw was sitting on virtual chair and things happening around you.. or the chair slowly moves through environment with deliberate and smooth velocity.
With VR, it's a combination of frame rate and as the comment above mentions - too much movement. In No Limits 2 rollercoaster for example, you can walk around the park and get on the coaster, ride the coaster, then get off and walk around again - it's too much. The best VR I saw was sitting on virtual chair and things happening around you.. or the chair slowly moves through environment with deliberate and smooth velocity.