Gamasutra had an interview with Epic Games founder Tim Sweeney, one of the things they talked about is how long it will take for games to arrive that will look 100 percent realistic like a movie. We've come a long way in the last fifteen years since Doom was released, and Sweeney predicts it will probably take another 10-15 years until game developers are able to create games with graphics that can't be distinguished from reality.
There are two parts to the graphical problem. Number one, there are all those problems that are just a matter of brute force computing power: so completely realistic lighting with real-time radiosity, perfectly anti-aliased graphics, and movie-quality static scenes and motion.
We're only about a factor of a thousand off from achieving all that in real-time without sacrifices. So we'll certainly see that happen in our lifetimes; it's just a result of Moore's Law. Probably 10-15 years for that stuff, which isn't far at all. Which is scary -- we'll be able to saturate our visual systems with realistic graphics at that point.
But there's another problem in graphics that's not as easily solvable. It's anything that requires simulating human intelligence or behavior: animation, character movement, interaction with characters, and conversations with characters. They're really cheesy in games now...