I agree. There might have been a time, early in its existence, where Apple could have created that clone market, and tried to compete with Microsoft as a software company on top of a competing commodity platform. But that was a long shot. The commodity PC was already a reality.
Apple is the last of the great *computer* companies (that is, companies that make both hardware and software). Interestingly, though, now that Microsoft has reached the limits of revenue extraction for software on commodity hardware, they are eyeing the idea once again of an integrated hardware/software bundle to improve the user experience. So it's not certain that the market isn't going to cycle around again in some interesting new ways.
In any event, I agree with the previous poster that Apple's genius has been as a hardware company, with software that seamlessly integrates with that hardware.