2000 was great. When XP came out a lot of people complained about how they added bloat and pointlessly screwed with the shell. (By this I mean explorer, not how Unix users understand the term "shell".) I felt that way too. XP got a little better as hardware improved and SP2 fixed some issues, then Vista made everyone forget what they hated before and suddenly XP was the "lean" one.
(Actually the more likely explanation is that the 2000-using XP-haters and the XP-using Vista-haters are not the same people. Maybe the former group gave up and no longer cares about Windows.)
You nailed it, it's kinda like when a Windows version came out. 2000 and Millenium were bad. XP was great. Vista was bad, SP1 was better and SP2 was great. People just remember Vista without the SP's. Windows 7 was what i needed, but that seemed like SP3 for Vista, only they named it Windows 7.
Then you have Windows 8, which will probably go a similar way like Vista did.