The Power architecture is still pretty awesome for raw power. But it's not designed for low energy consumption (ie: laptops). So while a desktop with some P6/P7 chips* would be an awesome beast - a laptop might be a toaster.

The G5 was a Power4 chip of some sort from memory.

Jobs read the market well. The move is definately to Laptops / portable devices - and Intels chips were much better at that.