What about the secret world online mmo? I have never actually played or seen it in action but every article I read about it raves about the quests in that game. Apparently it's a genuine mystery solving type of quest system, not the generic kill this collect that type of quests. It's a modern-ish setting though (like the clothes you wear look like irl clothes) so it's not my thing at all.

Currently waiting out on tree of savior myself. If that one's any decent I'll start playing that instead.