I think that right now, the emphasis is on how realistic it can get but that will be replaced by different graphical styles. This can be seen in paintings going from realism to impressionist, etc. and, more recently in action films that went from realism (until that has mostly peaked) and now it's bullet-time or other styles used to make it interesting.

I think it would be amazingly cool to, say, play a virtual reality/holodeck game in a painting or something.

Yeah, this is the obvious next step. You see it already with games like Legend of Zelda: Wind Waker - a surprise move away from better 3D cartoon graphics, and instead going for cel shading.

- David Stein