i get motion sick fairly easily in general: curvy or hilly roads (esp. as a passenger, it can even get to me as a driver though) or reading/playing video games in a car (and trying to get something at my feet at all while in motion), take-off and landing in an airplane (and if it's a turbo-prop, i'm nauseous the whole time) - i can play some games in the air though as long as there isn't camera control or 3D (as in 3DS, not necessarily 3D graphics), being on a boat in the ocean, and anything that makes me spin - rides or getting drunk enough for 'the spins' or even that one Everclear music video that just rotates the whole time.
so in video games, i have had it a few times but i try not to. first time i remember was trying Ridge Racer on PSP. something about the high speed plus being a handheld made me nauseous in less than a minute - and i love F-Zero so it isn't the high speed or crazy tracks by itself. also on Metroid Prime 3 if i set down the wii-mote before pausing, which causes my view to continuously rotate. last time was caused by low FOV in Metro 2033 - i played it for the first time for like 1.5 hrs or so, and although i felt a little weird while playing, the instant i stopped and looked away from the screen, i immediately became very nauseous and remained so for the next few hours. i increased the FOV via the .ini file, but it has kept me from seriously trying again until i'm fairly certain it won't happen again - it was seriously very unpleasant and i'm pretty sure it wouldn't have helped to 'give in' to the nausea. and it isn't like i haven't played a decent number of FPSs, but just not on a 22" widescreen 1080p monitor from 12" away.