I blame it on Sony itself for buying Toshiba and IBM's bullshit that a 1 TFLOPS CPU was possible as early as 2004. Yes, really. The entire Cell project thing was known since 2001. Also, trusting the extremely shady Rambus to deliver 1-2 GB of affordable and super fast "Yellowstone" DRAM by then.
So, that's quite an early point of divergence. Almost everything would be different, including the CPU of the X360 console.