The Xbox 360 is, as is the Wii and Wii U.
Arguably, the PS3 is not. The PPEs are, but the SPUs aren't. Unfortunately, in order to get decent performance out of that system, you need to take advantage of the entire processor including the SPUs. So it's not strictly a PowerPC system.
Fun fact- the original Xbox 360 (Xenon) developer kits were PowerPC G5 towers with ATI GPUs installed. I've always wondered if these systems were capable of playing retail Xbox 360 games, or if they were just released by Microsoft for developers to get the feel of the PPC architecture.
-SC