itch.io

If you have enough space (around 25GB total) and time (took me 38 hours in-game), I recommend The Harem Hotel which I believe to be the best adult game on itch.io. If you're looking for a game similar to this one, check out Eternum or Projekt: Passion.

If you want a longer list, I have a compilation of around 20 games here: https://itch.io/c/2972241/best-adult-games-of-all-time