Tried to write about my experience with early porn-games, and finished like "the history of porn-games as witnessed by me". Ok, whatever...
So, my first "porn" game was a strip poker that I played on ZX Spectrum at the age of, don't know, around 7 y.o. Then there was a DOS game, where you should name words by guessing letters, and if you fit within a specific number of tries - you'll see a lewd pic.
First real porn-game was "rendezvous with a stranger" - an early 2000th game similar to modern Ren'Py titles, that was using live-footage instead of CG renders. More erotic then porn.
Then, by the middle of 2000th, I found text-based games on TADS, INSTEAD, RAGS and QSP, the first I played was "The camping trip" by goblinboy. It used text parser, so you had to actually type commands like "go west" or "remove panties from <girl_name>". I actually liked the concept, it gave a good feeling of interactivity. That was also the time that I tried making my first game, using a Lua-based text engine called Milena. That didn't go well, as I wasn't able to work simultaneously on both story and programming. But I still have warm feelings towards text games and glad that genre is alive even now.
That also was time of web-based flash games hosted on sites like playforceone, hornygamer, the-shark-lagoon and pusooy. Shark's lagoon is still active and making games ... and they still have that mid-2000th look.
Then there was end of 2000th and modern age of porn-games began. There were different VNs and games from Illusion. If I could play browser games stealthy and no-one cared, it wasn't so easy with fullscreen Rapelay or Jinko Shojo - but I managed and never got caught, hah. It was also time when Violated Heroine and Corruption of Champions emerged, as well as other already forgotten titles like Flexible survival and others.