There's an interesting op-ed article that contrasts Call of Duty 4 and Crysis. The author argues that emergent gaming (player-oriented, as in Crysis) is the future. Scripted gaming (like CoD4) is the current norm, but it limits the player in a number of ways. Unscripted gaming opens up a world of additional possibilities, at the cost of a much more challenging development paradigm. I certainly hope that games become more unscripted over time; I had a lot of fun with the Crysis demo, and the unscripted work going into the Half-Life 2 world seems to really be paying off.