Actually, when we ported Aztlan Dreams to iOS some time back (we haven't finished doing so though), even with complex AI using multi-threaded approach, it ran pretty well on iPad 2 - even faster than on Eee PC with Intel Atom CPU. The end result "felt" the same as on my older laptop with Core 2 Duo T7700 CPU. Therefore, I don't think mobile CPUs are so far away and I don't think your comparison with Voodoo 3 or Pentium 4 is accurate.

For instance, many PowerVR 5 series chips have 1000 mpixels/sec, which comes close to GeForce 6200, but they have much better architecture and process shaders quite efficiently, not mentioning Tile-Based Deferred Rendering.

Again, this does not compare, for example, to my high-end desktop system with Intel Core i7 2600K, Patriot 2133 Ghz DDR3 RAM and Asus Radeon 6870 GPU, but for general population, even Eee PC with Intel Atom will suffice; therefore, SoC on typical mobiles will be more than sufficient for most tasks, even some gaming.

I myself felt this when trying to sell my latest Core i5 laptop, almost new, on MercadoLibre (equivalent of eBay): I had to give it almost for free and it took me 3 weeks to sell it; but when selling my used/scratched iPhone 3GS almost at stock price, I sold it in 2 days! If OEM retailers are having the same luck as me, it means PC market is in serious trouble!