For video games, the CPU architecture is still very important.
Remember when Halo came out on the Mac, and it was running slow as molasses on higher-performance hardware than what the game was originally written for? That's in part because many of the optimizations that make code run faster on x86 did the opposite on PowerPC. And any code that relied on SIMD instructions would likely have to be rewritten from scratch.
I'm not particularly familiar with the Cell architecture, but based on what I do know I suspect that going between it and x86 would be an even bigger headache.
Remember when Halo came out on the Mac, and it was running slow as molasses on higher-performance hardware than what the game was originally written for? That's in part because many of the optimizations that make code run faster on x86 did the opposite on PowerPC. And any code that relied on SIMD instructions would likely have to be rewritten from scratch.
I'm not particularly familiar with the Cell architecture, but based on what I do know I suspect that going between it and x86 would be an even bigger headache.