The most recent OS Apple has put on their website for official download is OS 7.5.5(7.6 came after Steve Jobs came back onboard). 9.2.2 is there through a back-door work around that I'm not sure Apple intended to be available, but is none the less there. Even so, OS 7.6-9.0 are missing(8.1, 8.6, 9.1, 9.2.1. and 9.2.2 are all there as updates, not full versions, but these were always free).
BTW, Microsoft supported Windows 1.0 through 2001. They offer a "downgrade" option on current Windows licenses, and I'm pretty sure you could buy Windows 8.1 and request a copy of Windows 1.0(even though no one would do that, as legitimate copies are less expensive than Windows 8.1). I've recently heard of people doing just that when they needed a copy of Windows 2000.
I'm not a Microsoft fan, but they are much better about providing legacy support than Apple. We have an instrument computer in the lab running Windows 2000. I was cussing at it yesterday(not an easy thing to get out of me, but yesterday was one of those days) because I needed data from it and it wouldn't read any of my Mac-formatted flash drives.