I brought up 98 as since it was rushed and so fouled up they had to release a new version of it (Win98SE). XP was rushed, and we know the issues it had. Vista, unless you have the "right" hardware, is a pain.
Win2k was good, I liked that. It was nice and stable and would cause hardly any issues so how they made such a howler with they morphed that into XP is beyond me.
Win 98 was a significant improvement over 95, and 98 SE was more to introduce additional functionality rather than correct problems. Win98 was built on 95, and there was no real pressure at the time to rush anything out. It was a new "name" release to clear up the ridiculous situation about the number of versions of Win95 that existed - there were at least 4, IIRC.
Win 2K was rushed out because of the millenium and the tie in with Server 2000 and the introduction of Active Directory.
How many Service Packs did Win2K have in its short life? 4 in 3 years? XP is on 2 after 6 years, although I accept that SP3 is overdue. Again, XP was an evolution of Win2K - there were much greater architectural changes from NT4 to Win2K than from Win2K to XP
95 and 2K were both rushed, and 98 (& 98SE) and XP respectively were superior OS's, both in terms of functionality and stability.
As you say, let's not mention Win ME. I'm still trying to figure out the point.
Having said all that, the 16-bit Windows family (95-ME) was cr@p, however much better Win98 was than 95. It was just a question of "less awful".
SD