I have argued many times that it is more likely that Nintendo and/or Microsoft would have GPUs with similar performance to a laptop GPU than something from the desktop side of things; and it is likely that Nintendo has a GPU between 500 GFLOPs and 750 GFLOPs of processing power, while it is likely Microsoft will have a GPU with between 1TFLOP and 2TFLOPs of processing power.
The actual chip Microsoft chooses will largely depend on what price range they want to target at release and whether they want to bundle Kinect (or something) with the system. If they're targeting $300 unbundled I could see a 1TFLOP GPU, and if they're targeting $500 bundled I cold see a 2TFLOP GPU.







