@Iggy
Asthetically, Windows Vista is the best looking version of Windopws.
I think the same. This is all subjective and a matter of taste, but IMO Windows 8, 8.1, and 10 are quite ugly. I can see some of the appeal of the flat look, but I think even recent versions of mac OS have taken this too far (the close/minimize/zoom icons, for example). I prefer subtle gradients, highlights, and shadows.
Amiga OS 4.x is maybe too close to Windows XP, but all they have to do is dial that back just a bit and not go entirely flat. It still looks pretty good, considering how long it's been out there without visual change.