From technological and imaginative point of view.
Intimidation, persuasion and taunt depends on my acting.
Make a move and defeat 2 in one blow.
Kneel before your enemy and admit defeat.
I can't stop my imagination when it comes to NATAL.(I dreamed this crazy battle scene with 1000 NPCs, in the middle you and your co, making Double Dragon movements, throwing axe moments, picking weapons from ground, switching weapons from your belt... Yes, I am crazy.)
But off course there is no way it could work this good. I've never seen any gameplay innovation for past 10 years except Wii and Portal.(late but nice attempt, Prey. And speaking of 3DRealms, where is my DNF?)
I mean there were few innovations. But few is few. Even on graphics department we have few leaders but at least there is progress. And AI, while should be the most important aspect of a game and relies on CPU power, never developed since. We are still there with 386 DX AI power. They come, stand, shoot at us. If they are melee, they just run at us and attack us. If they have proper line of sight, consider yourself lucky. This hasn't changed in 17 years of my gaming experience...(Bots better than Quake 3. NPCs more aware than Thief(1998)'s. Still waiting.)
Natal could be the missing link.