i think the motion sickness is caused by the SPEED of the game.....
in worlf3d, doom, and quake my motion sickness was really bad when playing single player... when i do multiplayer (speed of the game is a lil slower), everything was fine....same thing with counterstrike...i never get sick playin over the internet, but after playin or watchin someone else for 5-10 mins, i start to get sick....
all this time i thought i was alone on this, but i guess theres lots of people still in the closet....haha....
my friends always make fun of me cuz of this