WinXP with the "classic" theme was the best. Its default theme was goofy, but changing it took all of 10 seconds. Compared to Win2k, there were some minor improvements.

Up to Win2k, I don't recall new releases of Windows leading to people lamenting the UI changes; I do remember people not liking the initial look of XP, though. Maybe it's just because complaints got more visible after the Internet became popular, though. But even now few people seem to have strong preferences for, say, Windows 1.0 (… which was pretty much a TUI, IIRC)