I’m going to say Win8 & 8.1.
Say what you will about the UI, they did great work on the underlying kernel, file system and APIs. If they’d continued to refine it, it’d be damn near perfect.
They really started to lose the plot with 10; it kept a lot of what made 8 good (and steals a lot of goodwill from 8) but you can see the adware and telemetry start to creep in.
The next best I’d have to give to Vista, which also did some much needed revitalization, only to see 7 get the glory because Microsoft flubbed the hardware requirements and vendors were sloppy with drivers.
My favourite is NT3.5: full microkernel, no GDI in kernel space, no printer drivers in the kernel, less registry issues. We’d have skipped a lot of pain from the 90s and 2000s had Microsoft not went backwards with 9x and NT4.
Anyone have that gif of Rupert Murdoch with a plate of cookies?
Found it…