how intense most game are

It's due to something called "cognitive load" and even if you don't experience explicit discomfort it is somewhat related. Not only is there much more being thrown at you, but all of the limitations VR suffers from in stimuli (clarity, fixed focus, distortion, audio, vestibular, haptic, etc etc) and all of its interactive limitations result in an experience that is much more "difficult to process". People often feel like they are overloaded in VR when it's even the most basic experience. Now throw them into an intense game and it can become completely overwhelming (on top of discomforting most).
 
My suggestion is: try some simpler stuff, especially social experiences, and/or wait a few more years for VR to mature.