Too many are saying Skyrim... but then again, it is the same with me. I don't think I've ever done anything else. It was deflating to see Skyrim NPCs screwing so stiffly.
I look primarily for immersive experiences rather than writing in games. I make the exception for VNs on a rare occasion, such as Higurashi or Katawa Shoujo. And yes... porn. In either case, I generally prefer a comedic tone.
Tons of porn galleries available if you just want that. Stories are a must. Hell, the best porn games I've played are the ones I couldn't care less about the porn. I got invested into Eternum to the point that I found the sex scenes disruptive.
I'm partial toward gen 5 in general, but given the nature of this site, I'm going to pick Gothorita. Though I also appreciate Gothita for her odd resemblance to Betty Boop.
Caesar 3 for me. I adore that game, but Augustus adds so many QOL improvements. I guess I would also add FNV as a dishonorable mention, as that game crashes way too fucking often without a few basic mods. But in general, if a game requires modding for me to enjoy it, I'm not playing it. Too many...