Once Mac went to the Wintel architecture it was pretty much an admission that their previous systems could not compete against the speed and cost of the Intel based systems.
The Mac GUI is too cutsie for my taste and was a fan of Irix from SGI. Even SGI couldn’t compete against the Wintel design and has abandoned their Irix based systems and has since filed for chapter 11 bankruptcy.
The spartan, grey-themed OS X desktop is more cutsie than the Crayola colored Windows theme with all the little web-like links and pictures everywhere?
For processors, for a while it looked like MIPS might even win over x86, with MS making Windows NT for MIPS. But then Intel pushed x86 fast enough so that the performance difference wasn't worth the price premium. After that, nobody was willing to invest in R&D for those other processors and they died in the face of Intel's economy of scale, and especially the switch to the lower-power Core series (which is what got Apple onboard).