It is incredible just how widely held the view is that Win2k (or XP in classic mode) was close to peak desktop UI. (Contenders also being Tiger to Snow Leopard and Windows 7).
A key problem is that big US corps have always had a product design mentality that can produce monstrosities like your average cable TV remote and think it is in any way a good solution. That was clearly already an influence on things like XP.
Win XP was excellent, as was Win 7 I thought. However, since then KDE has in my opinion, gone even further and become even better. So, the peak is not gone, it has just moved to KDe.
Classic Mac OS' Platinum is also a contender for pre-2000 peaks. I actually never grew up with a Mac, my first one ran Tiger when I was in high school. But over the years I have collected rare or interesting Macs of yore, from before my time and come to adore Platinum and the classic Finder.
