This is a followup to @SorosFootSoldier@hexbear.net 's recent thread for completeness' sake.
I'll state an old classic that is seen as a genre defining game because it is: Myst. Yes, it redefined the genre... in ways I fucking hated and that the adventure game genre took decades to fully recover from. It was a pompous mess in its presentation and was the worst kind of "doing action does vague thing or nothing at all, where is your hint book" puzzle gameplay wrapped in graphical hype which ages pretty poorly as far as appeal qualities go.
So many adventure games tried to be Myst afterward that the sheer budgetary costs and redundancy of the also-rans crashed the adventure game genre for years.
Red Dead Redemption 2 Online
Yeah I know there were a lot of complaints but there weren't enough. The Player vs Player part of that game could have been fun, but it's literally the worst competitive multiplayer I have ever played in my entire life. Holy God how could it be so bad?? Nothing happens, you just get instantly headshot and thrown back to instantly respawn 100 yards back, forever, and ever. I call it Headshot Sisyphus 2