My first one was Robouzu. sadly i can't find the endless days version of it anymore. As for first AVN it was My New Family. decent but too many girls to build a decent relationship with them, and unfortunately looks like My New Memories is going down that same route along with making the smols non-LIs.
Originally only knew about Nutaku, so I played a few of the games on there, mostly Fap CEO. Those games are actual dogshit though and I knew it. Found out itch had NSFW games, and played what I consider my first real NSFW game, Harem Hotel. Loved it at the time, although now I would say it's mid to high tier in terms of stuff I've played. Enough itch browsing and I discovered f95 where the massive repository of gaming was. Some game on there eventually hinted at this sites existence which I now use for my NSFW gaming needs.
I don't remember the first time things got ugly, but when I think about the pleasure it gave me after things started to get ugly, I can say that I enjoyed the part where things got ugly a lot.
In the past I have played a few NSFW flash games and mobile games that I cant really remember the names of, or much about for that matter. First proper NSFW PC game i played was Sisterly Lust and many others since then.
Mine was Summertime Saga, and that was years ago. Game is still going on and now they have some new revamp updates going on, but still the same game, big oof.