Way back when IGN did a piece on the growing trend of morality-based gameplay. Those were the days when Splinter Cell: Double Agent asked if you'd like to waste long-standing amigo Lambert, and we were just getting early word on a little game called BioShock, with its option to destroy or save children for fun and profit. Exciting times. More freedom of choice meant making tougher choices, and that made for interesting gaming.
Three years later, the biggest game on the horizon is Activision and Infinity Ward's Call of Duty: Modern Warfare 2, and they're playing by harder rules.