I was reasonably happy with the NT 3.51 -> Windows 2000 -> Windows 7 line of Microsoft products. I skipped Windows 95, Windows 98, and Windows XP. By Windows 7, Microsoft had finally figured out how to make it work, had dumped much of the DOS-era code, and had the consumer and pro versions unified into something good.

It's been downhill since then. Ads, subscriptions, and trying to make desktops look like phones.

Windows 7 is still 12% of the installed base, and that's not counting the ones that don't phone home to Redmond.