Thanks for starting this topic Kevin. %)
The C64 is an 8 bit CPU (MOS 6510 @ 1MHz).
The PS3 uses the Cell processor. I believe that it is based upon the PowerPC architecture. It is an 8 core CPU o.o
One core is supposedly a full implementation of a CPU -- kind of like a master core. And the remaining 7 cores are supposedly partial CPU cores -- designed to be used for more specific slave tasks.
The X360 uses 3 complete PowerPC cores -- not sure if this means a single 3 core CPU or 3 independent CPUs.
I believe the Wii uses the PowerPC processor too.
Hence, if they are all using PowerPC architecture, then they are probably all 64 bit capable CPUs.