Well, in my opinion, from what I saw of it, FFXII was probably... hmmm... okay, the problem with comparing to other RPGs I played in the past is that they have that effect of nostalgia connected to them, so to make it an equal comparison I have to take my view of them down a rung or two. That said, I'd say that... FFXII probably equals CC, is almost as good as CT, almost as good as the Knights games, equal to FFVI, and is better than any other one that I've played and not mentioned.
CC is equal in dissimilar ways - it has a better mood and feel than FFXII manages to achieve - however, for other reasons, FFXII pulls ahead, and so in the end they equalise.
CT manages to stay ahead of it purely for its simplicity and mood, the very things that make it a classic.
The Knights games, well, their stories outmatch any Japanese RPG I've ever seen - in subtlety and power - and their music is excellent, and their voice acting wonderful. If only George Lucas would hire some other director to make these games and that era into movies, Star Wars would be back in its glory days. Now I know some people might try and throw at me certain games like, say, Xenosaga, as an example of a good story (mind you, I'm limited here by the games I have played, so that's why I say 'that I've seen'), but I found Xenosaga's story... ill-contrived, for several reasons. It didn't strike me as good storytelling by a longshot and, frankly, seemed amateurish more than anything (after all, anyone can throw in allusions that supposedly sound 'cool', but they didn't come together... and allusions like that do not make a grand story!) CT is simple storywise, but for several reasons (chiefmost being the out-of-the-blue inclusion of Zeal, it's ahead of the pack.) CC... too complicated a story. It makes sense, I know, but it got lost in its own complexity, and really... a story shouldn't be quite that confusing. It had its flaws. Let's see... FFVII struck me as, well, nothing special. FFVI was pretty good, but didn't match Knights. As far as I've seen, though, FFXII was doing a good job in its story. Alright, so it was cliched, but it used its cliche well.
Anyway, yeah, so from what I saw, I rank FFXII highly. I particularly like the voice-acting for Balthier, and I like the character of Ashe... okay, I've only played FFVI, VII, and X, but out of those, VII and X had no really good female characters. But VI had Celes. And Ashe is the closes I've seen to Celes.
