Games.
Other than basic things like Tetris (Quadrapassel) and minesweeper, I’ve not yet found an open source game I’ve enjoyed nearly as much as the countless proprietary games I own and play.
OpenTTD is the best in its genre if you like that sort of thing… Though it is a reimplementation of originally proprietary software.
Steam and Spotify, I just can’t get rid of them. I tried to download some music from YouTube, but the way to discover new songs is just way easier on Spotify than doing it yourself. Steam seems obvious, to play games, you should buy it, to thank the dev’s.
Affinity suite over any of their open-source competitors. I love Krita for painting, but for image editing, Affinity Photo is just so much better-suited and unlike Gimp, it’s modern, actively maintained and has a much more thought-out workflow. I heard that Inkscape was fine, but I personally didn’t like it either (but then, I also didn’t really like Illustrator all that much, it’s really a fully subjective opinion). But even if you did like Inkscape, you don’t have the seemless integration between the products as Affinity does. You can create pixel graphics in Photo, import them in your vector graphics in Designer, and can seemlessly embed any of the two into your documents in Publisher. And each program has a special mode (“persona”) that gives you the basic functionality of the others, and the UIs and workflows generally feel very similar and unified between them. For the hobbyist who doesn’t want to pay for an Adobe subscription, it’s truly unbeatable and the only reason I still need Windows every now and then.
Microsoft Excel - I tried a lot of the FOSS office suites but I always come back mainly due to familiarity but also compatibility (which I know is not much of an issue lately).
Google Photos - I have Immich setup and use it but my wife and people around me use Photos and so I have to conform.
“Pixel OS” - I can’t move to Graphene or similar due to banking apps.
Skype - Like Photos, due to relatives
Visual studio code. There’s nothing else that’s anywhere near as good that doesn’t cost money. Those annoying terminal text editors just don’t do it for me. I need code autocomplete and do not understand how there exist people who have the patience to get by without it. I do not have the time to be switching tabs 20 times a second because I can’t remember function parameter overloads. That intellisense autocomplete is just too good.