I also vote for Betrayal at Krondor as the best example.
Before that the best you would get were Ultima's extremely limited keywords, or a bunch of paragraphs in a manual that felt like something straight out of a generic D&D module, like Temple of Apshai.
Neal Hallford's first game, Tunnels & Trolls, is text-heavy and well written but it's just a fancy CYOA:
Ultima IV has a far better plot than FF4, but FF's delivery is miles ahead. There are no real conversations in U4, you basically just get exposition and riddles one after another.
I mean, this is dialog in FF4:
ROSA: What happened? One second you're being sent to Mysidia, the next you're being sent off to kill some ghastly monsters. And you've been acting strange since you came back.
CECIL: No, it's nothing...
ROSA: Then please don't look away...
CECIL: In Mysidia... I killed innocent people, plundered their village, and stole their crystal, all for what?! Why did I do such a thing? It's as if my heart has become as dark as my armor!
And this is Ultima IV:
PLAYER: NAME
IOLO: Iolo
PLAYER: JOB
IOLO: I play for the people.
PLAYER: PLAY
IOLO: I play my lute and receive the good wishes of the people.