ME was unrelated to 2000. WinME was the last release of the MS-DOS-based Windows familiy -- from 1.0 through "ME", Windows was not an operating system, it was just a GUI application that ran on top of MS-DOS. Useful as they were, even for business use, those MS-DOS-based releases were glorified toys. WinME was intentionally broken and unstable, because Microsoft knew it was the end of that line, and it needed users to quit that family and migrate to the new family...
The non-MS-DOS NT ("New Technology") family was started in the early 1990's as a "serious" operating system. Those releases started at NT3.1, then NT3.5, and NT4. NT5 was scheduled for release around Y2K, so the MS marketing department christened it "Windows 2000", but I still have the earlier documentation where it was still named "NT5". A year or so later, NT5.1 was released and named "Windows XP".
NT6 became "Vista"; NT6.1 became "Windows 7"; NT6.2 was "Windows 8"; NT6.3 was "Windows 8.1". Then they skipped a few numbers for the heck of it, and made "NT10" which was named "Windows 10", and here we are.
> And Apple's numbers are just the phones, not the OS's.
Oh, geez, color me embarrassed, I didn't see that. I was thinking MacOS releases. D-uh! and thanks for the correction! :-)