A look at the different psychological profiles of game players, and how to adapt your design accordingly:

http://whoseturnisitanyway.com/design-player-psychographic-profiles-part-1/

http://whoseturnisitanyway.com/design-player-psychographic-profiles-part-2/

http://whoseturnisitanyway.com/design-player-psychographic-profiles-part-3/

http://whoseturnisitanyway.com/design-player-psychographic-profiles-part-4/