Its funny cause a lot of what "PS2 did that was revolutionary!" was already done by Final Fantasy 2; just, you know, it was never released here, but doesn't change the fact that FF2 did it first.
Except FF2 had a coherent story the entire way through; the only thing that made Nei a "main character" was that she was forced into your team the entire time til she died. The utter lack of plot scenes (like, I mean REALLY lack) from after that guy blows himself up until...well, she dies kind of makes it hard to give a shit. I don't mean "there are a few plot scenes"; I honestly don't remember a god damn scene between beginning of the game and Nei's death outside of that one with the guy who blows himself up with his daughter, which was more "..." than anything else.
As far as I'm concerned, FF2 is the revolutionary game for the Genre's plot. It did a whole lot of shit that it doesn't get credit for (admittedly, i know its hated for gameplay purposes, but shh!) Not being released in the US kind of hurts it, but doesn't change the fact that it did them first.
It has characters, actual character interaction (not just "we have names and a plot scene where we are introduced!" like PS1, for example), an actual villain with screen time (not a lot, but it beats "Rar I sit on my throne til you kick my ass!" like Lassic), plot twists, and doesn't just kill off one character, it kills off at least 5, admittedly no one cares about Scott preSoul of Rebirth, so really its just 4 characters. It also had this concept of a Princess who actually did shit instead of just get kidnapped (Oh, Hilda gets kidnapped, sure, but she does stuff BESIDES that.)
Also had plot flow that made sense. "The empire is kicking our asses partially cause of better stuff. If we had MIthril Items, we may stand a chance. Firion, your next mission is to find Mithril!"
Oh, also the Password system did lend itself to a degree of REAL role playing, more so than most JRPGs really, sadly didn't return (though can sort of understand why.)
I'm not saying FF2 doesn't have its issues, but its hard to call "Phantasy Star 2 revolutionary!" when FF2 beat it to the punch in almost every category, and did it better too (having actual plot scenes and dialog, not just "Halo thar my name is Lutz! Now go find these legendary weapons so you may kick the crap out of Mother Brain, k thx bai!") PS2's ending is about the only thing new it did.
Really, compare RPGs of the SNES Era and later, and tell me what they resemble more: FF2's plot style, or PS2's plot style.