I will do a lo-rez crash course in computer history over most of the past half century to make the point that the intrinsic quality of an OS seems to be what gives it staying power. By low-rez I mean I am clipping out lots of bit players or companies that are redundant in the big picture.
In the mid-1970's, when 8-bit microprocessors first came out, there were two kind of computers.
CP/M computers (Imsai, Altair, Processor Technology)
one-off computers (PET, TRS-80, Apple II)
The CP/M computers all used the same 8-bit OS which was in spirit, and some say body, the precursor of MS-DOS (born "SCP-DOS" since Microsoft licensed it for $60K instead of writing it themselves).
When IBM invented PC who made the BASIC used in almost every microcomputer at the time. Microsoft had no OS so they license SCP-DOS really fast and then rel-icensed it to IBM for a low-rate per system that quickly added up.
CP/M died pretty quickly after that, taking the 8-bit systems with it and some 16-bit systems that had moved up to CP/M-16. They pretty all died together. Moral is, if you are different brand computers who share a common OS and the OS becomes uninteresting you ALL become uninteresting at once.
The Commodore PET was replaced with the Amiga (which died ages ago), the Apple II was replaced with the Macintosh - and the TRS-80 went threw a few iterations, then became a PC clone and then went away.
I will limit discussion of minicomputer to just this: they had Unix and they had one-off operating systems.
Just before those microcomputers were around, there were mainframes. IBM had mostly batch systems that were appalling, Univac, Sperry, Control Data Corporation, Cray, etc. And a computer named Multics that had a secure, interactive operating system which Unix was loosely based on. These brands had their own OS except for one little anomaly.
A company named AMDAHL made an IBM mainframe clone (yes, but do not freak out yet). AMDAHL and IBM feuded a lot, vying for customers.
http://en.wikipedia.org/wiki/Amdahl_Corporation
Amdahl's customers were allowed to license IBM's OS and run it on their computers. The reason was IBM had a monopoly (and acted like it) so they ran afoul of the DOJ. Amdahl computers were cheaper than IBM computers.
Anyway, history of the computer industry clearly shows there is no one "right" way for an OS to work. At any given point over the past three and a half decades, there have been some operating systems that only ran on the brand of computer who invented it and some that were mostly voluntarily licensed out to OEMs.
Apple II was way more foolproof & fun computer to use than CP/M computers. The Mac OS was way better than MS-DOS for doing white color work.
Multics was laid to rest in the mid 1980's having been sold to some very chic, though mostly discrete, rich customers. Sadly, Multics passed having never exceeded microscopic market share. However, the ripples it sent downstream early in its life shaped the operating systems and the computer security models we use today.
Unix, its heir, was kind of king in the late 1980's and early 1990's for business users and some hobbyists ran the one inexpensive commercial distribution of it.
Macs with System 7 were too slow in the mid-1990's compared to MS-Windows 95 PCs, and Linux was still a bit shaky. But by 2001, all 3 operating systems had found their legs and were coming out with new versions that got great acceptance in the market place.
Amdahl had faded away not being able to keep up up the relentless pace of IBM's hardware innovation, leaving IBM mainframes cloneless for the first time in a quarter century. IBM very roughly around this time introduced Linux to zOS, a fusion of several decades of proprietary mainframe technologies that runs on the 64-bit zSeries mainframes. It was the 64-bit zSeries that dealt the death blow to 31-bit Amdahl machines in 2000.
Today, about 70% of IBM PC clones still run Windows XP which came out in 2001. Macs all run much newer versions of OS X which came out in 2001 - and happens to be based on the widely used Unix OS. Linux systems run a newer version of their kernel and share decent OS API compatibility with Unix and Mac OS X.
There are drawbacks to each of the 4 OS's that dominate today and they each have their strengths as well. There is no moral or practical reason for determining whether a computer maker or system-less OS vendor makes a better OS.
What determines of the OS is better or not is the OS - not some arbitrary rule. Quality seems to translate to longevity, and aptness to current market needs seems to translate to current market share.
