Detailed completionist checklists.

If I have cleared an area, I want to have it reflected in an overview screen.

If I'm missing an item, I want to know which enemy drops it, where I can find it, or how I can craft it.

If I need to pull out my phone to check a wiki, then the game has failed me.

There's something to be said for exploration games, and in those cases, the details should be obscured until the player has cleared 90% of the area, or gotten past the boss (or something like this).