I would say you are one to talk concerning this subject.
XII never received the type of backlash over here that it did in Japan. Japanese fans were bitching about this game before it released and even after. It basically had the same deal as over there as XIII had over here in that it got great reviews but the fanbase over there seriously backlashed against it at the time. It has certainly subsided since then but the game never received as much attention over there as over here.XII has never been listed as one of the top games in the series. It hasn't been "vindicated by history", it's just that XII's fanbase has coalesced into a single group, while those who hate it have moved on to other, better games. There is still a huge majority of gamers and Final Fantasy fans who will dismiss XII out of hand if you mention it. The discussion on it is largely positive because only people who like the game bother to discuss it anymore. Final Fantasy VI and VII still get haters because they are games that are largely considered fantastic by the majority of series fans (or RPG fans in general). XII has always been considered mediocre, so it is not a game that needs to be torn off a pedestal in the minds of those who hate it. Most people who dislike the game just moved on and forgot about it.
Also, while Lightning may not be nearly as huge over here as she is in Japan, there are still tons of gamers who list her as a favorite Final Fantasy character. FFXIII failed over here far more because of the linearity and nonsensical plot than it did the characters. A lot of the characters were incredibly popular. Snow, Sazh, Lightning, and Fang are all listed among a lot of people's favorite characters. Maybe not among the core Final Fantasy fans, but among a lot of gamers in general? Definitely so.
I'm not saying that XII is suddenly "the bestest game evah!" but it basically has risen from "worst FF" to "meh, it was okay" considering how often I see people talk about how they hated until they let go of their preconceptions of what they wanted it to be, and then suddenly realize in their next playthrough that the game isn't half bad, I'd say XII has more going for it than you wish to believe because it doesn't work with your own views.
XIII is certainly getting heckled by the Western fanbase and while the cast is a mix bag, it is pretty obvious that Japan loves them a whole lot more than the Western fans do. The West certainly hated the game design the most about XIII, but its characters and story also have been far more criticized over here than in Japan where it is just gold. Not saying this means "the West hates XIII" as much as I'm saying that the West doesn't like it as much as Japan. Not that the Japanese liked XIII as a game as much but for them I think the story and characters redeem the game, whereas the West is usually the one wishing we could finally move on from the series.
Yes the haters moved on from XII, but you know what? They haven't moved on from FFs like FFII and FFVIII which still get more revile than XII does, despite being around longer. So in my mind, that tells me that XII has certainly moved on up in the fan community. It's no longer dirt, it's now just the worms in the dirt. I feel you are simply trying to keep the fires of the hatred of this game lighted, and while I disagree with your position, I can sympathize because I will probably be in the same boat in a few years when XIII's stock gets raised a little better. For the most part, I will say that FFX is pretty much the last non-controversial FF among the fanbase. Starting with XI, each new entry has become more divisive than the last. Still as much as I love XII and hate XIII, I find it amusing that XI and XIV have probably been more vindicated by history than either game.