The whole "bits" thing is actually pretty interesting.
bits is actually about precision of the numbers, and 32bits is more than enough for 3D math.
A CPU with pure 64 or 128 bits just don't help anything with performance. it is only useful to map more than 4GB of memory.
SIMD shit makes 64/128bit useful for game math, because you hack the ALU to treat a say 128bit number as four 32bit numbers glued together and process the same operation (say an addition or multiplication) in a single pass.
This use a lot mess space on the chip than four separate 32bit math numbers and all the execution logic etc etc..
Since the N64, give or take (on it's co-processor), all almost CPUs can do SIMD, even in lesser systems like the 3DS.

But not the WiiU