While the layout of the menu itself changed some over the years, the base location in the bottom left has remained the same.
Even with Windows 8 you could get to the startscreen(?) by flicking the mouse to the bottom left corner. That would case a square to come into view holding a preview of said screen.
Not until Windows 2000. Prior to that, the Start button had a single "dead" pixel along the left and bottom sides of it in which clicking didn't open the Start menu. Microsoft design: it looks right, but it just doesn't quite work right.
http://blogs.msdn.com/b/jensenh/archive/2006/08/22/711808.as...
Though I think the Apple bar is starting to show its age with higher resolution screens becoming popular. With the latest macs, moving the cursor all the way across the screen is a bit tedious. Apple seemingly introduced wonky mouse acceleration to solve this, but it seems like they've introduced an extra problem.
Compare that to the lack of concrete UX decisions in the world's other major OS, unable to settle on a single menu style and so much flip-flopping on key features (cough-Start Menu-cough); removing them in one version and bringing them back in the next.
Is the Mac OS Menu a design that simply cannot be improved on, or are the users just not clamoring enough for a change?
[1]: https://en.wikipedia.org/wiki/Apple_menu