For me it was Dead Space 2 when I was 12-ish. For reference, at this point the most gruesome/gorey/violent media I was exposed to was the Halo 3 Flood levels and the original 2 Alien movies.
I had way too much fun playing it to be traumatized by it at the time, although when i was old enough to understand the horror of the whole "your memories and experience becoming food for a god-like being that has absolutely zero respect for your existance", that did inform my perspective of other media such as Evangelion or Childhood's end when I watched them for the 1st time.
What was your equivalent to this? I've heard the Resident Evil games are quite common for this but I want to hear your perspective.
I remember the first time I ever saw 7th Guest.
All I could think about, was this was the future!! The graphics (lol), oh man!! It was on a CD! That went in your computer
The game was kind of boring though, IMO anyways. Never really got into those 7th Guest, Myst games that deeply, as they could never hold my attention long enough.