In which case your argument fails, because the original argument was that FF2 did it -earlier-. In addition to having more plot scenes that generally strung together better. Honestly, FF2 manages to stand on it's own until, oh... probably mid-SNES era with the exception of DW4, which is better than it. I know the FF series doesn't manage to best it until FF5. I'm not going to comment on the PS series, because it sounds like 3 could be better, but manages the feat of even worse gameplay, which boggles the mind.
Phantasy Star 3 had some...interesting ideas, I guess, but the execution fails for all the same reason Phantasy Star 2 does:
Fundamental lack of plot scenes, and actual dialog. If you remember, characters never actually interacted much in Phantasy Star 2 outside of Rolf saying "That is a good name, you can join us!" to each new character, and I guess "Shir, where did you go?" This is the extent of PS2's interaction.
Phantasy Star 3 is, for the most part, no better, IIRC. The scenes are few and far apart, and its more monologue based than characters actually speaking to each other, so it feels more like you're being ordered what to do next rather than an actual story is transpiring...
Which is why that style fails.
Again, FF2 deserves credit for the things it tried and the style of plot it had is something that pretty much 90% of the jRPGs after it that at least attempt a half decent plot/characterization emulate (FF2 does not have half decent characterization; I mean games that attempt at it go for this style of plot), so relative to its time, it stands out. Like I said, FF2 didn't necessarily do this stuff WELL, but it sort of broke the ice, in a sense.
And i played through the original FF2 the entire way through, with a fan translation admittedly, but it still didn't have the luxury of a slightly enhanced script. It had actual character interaction; it was bare bones, boring, generic interaction, and frankly, it downright sucked...but its still better than a plot style where its one guy monologuing each scene, and telling you want to do (which sums up like all of Phantasy Star 2's plot.)
Basically, what I'm getting at is...
FF2 feels like a really badly written plot, but still a coherent one nonetheless.
PS2 feels more like you're just following orders OR the random path before you until your next dungeon, and nothing happens the entire game until the death of a character with no speaking lines until that scene (...wait, Nei may have had one line when she initially joins?)
And FF2 did a plot idea very few games actually attempt at (maybe cause its so hard to pull off properly? FF2 didn't do it right after all; again, FF2 tried at a lot of things, it seldom did them right <_<), that being the idea of an actual villain in your team.
By which I don't mean "He use to be a villain, but now he's good!" style, which lots of games do, or the "Good guy turns evil!" thing. No, Leon was actually, you know, evil the entire time. When he rejoins, he's really just helping you out cause you're the lesser of two adversaries, he himself still is a pretty bad guy. Again, FF2 failed at doing this right; I'm not gonna argue it, but very few games even attempt it, which is my point. Feel free to disprove me if I'm wrong!
As a random side note...
FF3's Old Men > all characters in the 8 Bit Era. *FACT*