Of all the OSes Microsoft put out, Win 7's UI has to be the best... though after a while it too got stale and needed dressing up with ObjectDesktop and CursorFX, etc.
Win 95 and 98 were okay but flat and in need of customisation.
XP was a bloody awful rip off of Fisher Price and it was essential to be customised.
Vista looked okay but after a while it needed dressing up to avoid UI-boredom.
Win 7: the best to date UI-wise.
Win 8: what was MS thinking with no Start Menu and that damned panel full of damned apps?
Win 8.1 was better but still needed work to make the UI acceptable, more pleasant to work with.
Win 10: Oh no, back to the Fisher Price look and a Start Menu covered in damned apps and advertising.
Of all the MS OSes, Win 10 is the worst on so many levels. Sadly, for many, that's all there is these days. Thankfully, some 3rd party developers have created software that removes many of the worst features of Win 10, thus bringing it back to a half decent, less bloated OS