As for Windows vs. OS/2 it's at best complicated. It's a bit like a micro-cosm of the PC vs mainframe debate. The raison d'etre of Windows 95 was backward compatability with a low memory footprint.

That may seem like a small thing, or at best not a thing to make so many enormous compromises over, but back then it was everything. The problem with doing multi-tasking "right" was that it imposed a ~4mb RAM requirement per 16-bit application being run at the same time. That is nothing today but back then 4mb was the minimum requirement for installing Windows 95, and it represented a cost of around $100 in 1995. Owning a computer powerful enough to run even a handful of 16-bit apps while running OS/2 or NT was simply above the economic means of a lot of people. And by the time technology caught up and RAM became cheap enough to make proper multi-tasking cost effective there was too much Windows 9x network effect for competitors to make much headway.