This is just off the top of my head, but let's give it a go. Security, across all axes you'd care to evaluate. Actually-working multiprocessing, including acro

This is just off the top of my head, but let's give it a go. Security, across all axes you'd care to evaluate. Actually-working multiprocessing, including across big/little architectures. SxS. A graphics subsystem that doesn't torpedo the computer if something goes wrong (and which continues to improve, e.g. DirectStorage). WSL2. WSA. BitLocker. Solid-state TRIM. Multiple desktops/task view. Aero Snap/Peek. The user-facing bits are emphatically not my favorite, but, even if I spotted you Windows 2000 so that you were on the NT kernel, there's a ton of stuff that's improved even from version to version, let alone over a twenty year gap.