"Apple should have licensed the Mac's operating system."
No, not really.
Direct comparison of the two companies' business models is - pardon the pun - like comparing apples to oranges. Seriously, Apple is a hardware company, like Dell or HP, and Microsoft is a software company. Just to be clear, hardware companies make their money selling hardware and vice versa. Not to mention, changing business models of this magnitude is not simple. (IBM, who successfully did this in the mid 1990s after a near death experience, is the rare exception.)
Apple appears to be the personal computer company that's been around the longest. Although a big chunk of Apple's revenue comes from the iPod how many other multi-billion dollar computer companies, after 30 years, are still selling what they sold on day one?
As an Apple shareholder, I much prefer comparing Apple, with its $78B market cap, to Dell, with it's $61B market cap.
(Yes, I know Apple did license its OS in the mid 1990s.)