01000101 is right that operating systems, in terms of market success, have to fill a 'need'. Microsoft grabbed a sizeable chunk of the business computing market share in the late '80s, and many users wanted to run the same software at home as they did at work. After all, if their company used DOS/Windows, then surely it's great for home users too?
And it ended up being "good enough". Sure, it was unstable and riddled with security problems, but Joe Average was writing his letters, playing his games and messing around on the interwebs. It did an adequate job. The Amiga was effectively dead by the late '90s, Apple was on its death bed too and widely perceived as too obscure and expensive, while Linux had only the geek mindshare.
BeOS was an opportunity to bring something genuinely fresh to the computing world, but Microsoft's strongarming tactics won the day:
http://www.internetnews.com/ent-news/ar ... hp/3073811
Microsoft is a very successful, bullish company. Yet it gave the cash-strapped Be Inc. $23m to avoid being challenged in the courts. Although legally Microsoft didn't accept any wrongdoing, the company's muscle flexed in many, many ways across the industry to prevent BeOS from gaining a foothold.
That's capitalism -- I don't harbour resentment to Microsoft for always wanting to win. But great OSes won't necessarily flourish when there's a very powerful player in the game.
M