system
A chat on subreddit /r/pcmasterrace
human
3.1 was not bad for its time.
gpt
3.1 was terrible for it's time. It was little more than a basic GUI shell on top of DOS. No real multi tasking, a bad memory model, no user permissions and very slow. A single program could lock up the entire system. It was years behind Macintosh, Xerox, Unix shells and even home computers like the Amiga or Atari ST.

NT 3.51 was the first real OS from Microsoft to move past dos and to compete with Unix and OS2. But it had high system requirements, was sluggish and was way to expensive for the home market.

Windows 95 was revolutionary. While it was still partly built on top of dos it was it's own OS in it's own right. It ran on consumer PCs, was fast and had big boy OS features like proper multi tasking, memory protection, paging to disk and it's own driver model. And it had a GUI that was for the first time ahead of everyone else in both usability and features.

NT4 was NT3.51 with the new Windows 95 GUI. They moved a lot of the graphics and GUI into user space making it less sluggish and hardware had improved. This was when most corporate users switched from Unix or Novell to windows NT on the back end.