http://www.gamasutra.com/view/feature/3868/shoot_to_thrill_biosensory_.php
Great article. I don't like that they try too hard to say that certain ideas WILL create certain emotions (such as a specific type of weapon, tutorial, etc.) but it's a good article about what generally people think when playing games.
I'd also like to see them test Mirror's Edge, Left 4 Dead, and some RPG's to see how the players feel after playing those games for a long time.
spoiler (click to show/hide)
(http://www.gamasutra.com/db_area/images/feature/3868/fig7.jpg)
lol