Xbox 360 is older than Core 2 Duo, high end PC was dual k8 at 2.4GHz +- when the xbox 360 was released, actually most PC gamers had single core K8 and Netburst at the time... the Xbox 360 CPU was somewhat impressive when released (late 2005/early 2006)
No. It wasn't. It had impressive numbers, but once you started writing code for it, the effect faded out really fast. It was the dumbest in-order speed-racer design released at that point, and it lacked basics like store forwarding. This meant that the second you deviated from straight-line code, it got really slow. By Microsoft's own numbers, you can expect about 0.2 IPC for each thread in normal game code. In the end, for most tasks the cpu was slower than the typical Pentium 4 out at the time of release. (There were a few things you could do really well, like mixing audio, but the gains were wholly lost on the parts of game code that it just ran terribly.)
At the tail end of the console cycle, advances in compilers, hand-optimization, and changes in datastructures made it not suck quite so bad, but at no point during the console cycle was it better than the absolute minimum PC cpu you designed games for.
same for the PS3 a year later, the Cell SPEs had some respectable numbers, considering it happened before GPGPU was really a thing.
The exact same was true for the Cell. It had impressive numbers, was a total dog in practice.