Gameplay wise?? Nothing, only the motion control stuff.
But many of the games worlds wouldn't have been as convincing and thus engaging. games like Assasins Creed would be gimped by poorer animation, fewer/less diverse NCP models and less believable cities. Discovering the alien world and species of Mass Effect wouldn't have been so enticing, nor would the using the biotics. The characters in Uncharted wouldn't be as lovable, nor would the set pieces pack as much as a punch.
I think people often undervalue how graphics/physics help make an experience more enjoyable.







