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.
You actually have a pretty cool taste in games. You seem to favor sandbox style stuff and RPGs. That's cool.
If you're into boomer shooters, the Hypnospace Outlaw devs made a Duke Nukem 3D style game: Slayers X: Terminal Aftermath: Vengance of the Slayer. It's hilarious. Zorch is also worth a shot.
You may or may not like Shadows of Doubt? It's still in early access, but it's shaping up to be really intriguing. Big open city where you're a detective solving mysteries however you may please.