Unfortunately, I think a much more likely situation is that x86 (/64) is only slightly hobbling things, and Intel are easily able to push past that with technical craftiness. As in many other cases, implementation trumps theoretical design.
A new architecture can offer that much advantage; x86_64 wasn't even the third most-performant implemented ISA when it was released, and every other ISA makes gains far faster than it. SPARC and POWER are still competitive with it despite having 1/1,000,000th the amount invested in them, and in just a few years and with comparatively nothing invested into it, RISC-V is starting to rival a portion of the chips (though not the upper line of them yet).
It "won" because of backwards compatibility, nothing more.
The evidence is that architectures are just not as important as all that. x86 is clearly pretty bad in many ways, but clever tricks and microcoding have been able to overcome those issues.
This is a complete misinterpretation of the above comment.
The issue was chipsets and peripherals, not POWER performance (which generally always beat x86 at the same point).
The problem was that the entire ecosystem was built around communicating with an x86. So, you couldn't get a Northbridge or Southbridge equivalent that was even remotely close in performance or power consumption to those in x86 space.
Unless you decided that you were going to take on everything in chip design, you couldn't compete. And Apple didn't decide to take on everything until Intel told Apple to pound sand and pissed Jobs off.
Do you have a source for this? First time I've seen anyone claim that the G5 was competitive with contemporary Intel CPUs.
Those were different times for Apple. The ship was noticeably turned, but the storm not over yet.
The 601 based PowerPC's were the first to be able to do 3D graphics on the microprocessor well.
The G4 based titanium Powerbooks were sufficiently better that they became iconic at a time that Apple wasn't regarded that well.
Sure, the G5 and up were disastrous, but the writing was on the wall well before that. Chipsets on the G3 and G4-based systems used more power than the processor and that only became untrue because the G5 was quite so poor.