Could the game not be run on your Mac, use its power and graphics card then operated and displayed remotely via AppleTV in the living room? Like VNC or something.
It certainly wouldn't use the Mac's graphics card. But if apple ever gets Quartz2Dextreme working in a stable way, it could potentially stream an interface directly from the computer to the AppleTV (assuming the AppleTVs graphics card is able to handle Q2Dextreme).
However, highly complex graphics games use a fair bit of bandwidth, AND networking will have a delay to it. Perhaps if the graphics requirements are fully separated from the computing requirements (as Q2DExtreme attempts)... but I have my doubts.
I had a bit of an out there thought.... I was thinking that one of the secrets to Leopard could be a new gaming environment. This turns every mac (prob intel only) into a gaming station. This would instantly put a gaming pltform into the hands of millions of Apple users. The

TV will provide the link to your Television and a Wireless Controllers will be used over your home network. This would be great added marketing for Leopard and also the

TV
The 'top secret' features of Leopard will be interesting. I'm betting on the remote interface Claymore asked about - I'm not so sure about a gaming environment though.
*** Does Apple need games?
I'm in 2 minds about Apple focusing on games. My first thought is "too difficult - they need to stay clear". However, like it or not, people are looking at their living room and for their entertainment needs are (to some degree) comparing AppleTV/Xbox360/PS3/Wii/TiVo etc. Add games, and DVR, to AppleTV and what a machine!... oh, wait, it's missing BluRay/HD DVD... There are quite large differentiators at the moment as multiple environments converge. How does Apple want to play its game?
*** What about CoreAnimation and Interactivity?
Interactivity and virtual interfaces are going to be huge, and that might be the biggest reason for Apple to get involved with games (develop their background technology). Games machines are creating virtual worlds and have a head start in interactive environments.
Rather than imagine games - imagine TV game shows with full interactivity so you can play along. Apple will, of course, have CoreAnimation and this is much more important than most people realise. I wonder how they plan on letting us interact with computers and the AppleTV - is it the same as they've demonstrated?
*** How would Apple get into games?
It's all far too expensive I think, for Apple to compete with MS/Sony/Nintendo. They CAN do the basic stuff as many people have said and that'll be enough in some ways. Playing chess, or risk, with family remotely doesn't require much processing power. I'm sure they could include an emulator for old AppleII games & DOS games with little effort.
Getting big games takes far more. If they want that - perhaps they could become a huge supporter of an open API for gaming - so developers write games once for Mac/Windows/Linux? (does such an API already exist and need some big names supporting it?).