Its false, for both the CPU and GPU.
Forza 3 has 10* the polygons and 4* the texture resolution along with other tweaks compared to Forza 2. Thats with just two years of progress, using the tessellation engine of the Xbox 360 GPU. Once developers get a handle on this technology, the Xbox 360 of tomorrow will put the Xbox 360 of today to shame. Epic themselves may very well be hard at work mastering this technology right now for Directx11 so when we see their next Gears of War iteration prepare to be blown away.
As for the CPU, it was released back when multi-core programming was a rarity. Pretty much all development was done with a single core CPU in mind and the programming model is still catching up. The Xbox 360 has 6 threads when most software designed today can only adequately handle 2. Just balancing the workload so that the two threads on a single core don't contest for the same resources is an artform in itself, let alone creating a game engine which can use all 6.
Tease.









