To me, XP and Vista looked like a terrible attempt at replicating Mac OS X when that all wow'ed us - it's hard to imagine these days just how big of a deal the iMac and later on OS X were in terms of moving away from grey boxes everywhere (though sometimes too far, since Windows 7 really toned down and refined XP/Vista's UI).

For me, I grew up on Amiga Workbench 2.0 and MS-DOS, so Windows NT/2000 felt like a good evolution from it's User Interface. Very functional, for sure.

100% agree on Classic MacOS. As outdated as the tech was, it was beautiful because it was elegant without being distracting.