I am a wargamer, we don't NEED awesome graphics in our games, hence they are rarely much of a drain on a computer to run them.
Even so, some games can be really demanding other ways. Gary Grigsby's War in the East (pc wargame) will cost you more processing power to run than any other game on the market right now. That's flat fact. I have the game, I already know this.
But, it takes a bitching video card to run some graphically intensive shooters at best visual appeal. The thing is, they don't always need a processor and as much muscle as some of my wargames that possess graphics that look like that came from the 90s.
The above mentioned wargame, playing AI vs AI, will conk out after being given about 15 minutes of automated play running on a good dual core with 2 gigs of ram with a reasonably decent video card. It simply can't perform all the calculations fast enough.
Graphics in a game, are only as good as the person that designed the game required them to be.
So some games made today will simply not look better if there was no reason to have them.
As our doodads get more and more powerful, your options get better and better to dump more and more into the experience, if the person making the game feels like using the muscle.
Best thing I have seen a computer do recently, is out perform hohum singers. I'm a total Hatsune Miku fan eh.
She's not better than Celine Dion or Enya. But you can cram Lady Gaga who sucks ass.