The Oldschool Runescape and Guild Wars wikis are still some of the best wikis I've experienced. Both of them are even implemented into the game. In GW1&2 you can just type /wiki <insert subject> and it'll open a browser tab to the wikipage.

In OSRS there's a button next to the minimap that you click on first and then on the subject and it opens the wikipage for it.

I wish Warframe would move to a osrswiki model. A theorycraft heavy game almost requires a good, performant wiki.

Somewhat recently Wowpedia moved away from fandom to wiki.gg, dunno yet if it'll be another fandom, we'll see.