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.
Metroid Prime. The game gradually felt like a chore, getting all the power-ups. After I killed the penultimate boss, I realized I had to get all the artifacts to fight the final boss. And that's when I said fuck it and stopped playing.
Remember the Tribals in Jet Force Gemini? I used gameshark to get all of them.