I was content to just lurk, but I actually had to create an account just to respond to this...
@FF6 v 7 (devil's advocate)
The narratives were pretty much on par with one another. A lot of the technological improvements in 7 helped create a sense of atmosphere that wasn't doable with 6. FF6 required you to imagination the level of ruination in the world--honestly, even in Narshe, Zozo, etc., it just didn't compare to the visualization of the Midgar slums. Everything that was darker was notably moreso, in contrast to the chipper protagonism of other games. Seven, at least in the U.S., was also one of the first to legitimately kill off one of your characters. (6's ending was much better though)
The gameplay was far more flexible and better fleshed out in 7 as well. Let's not forget the importance that has in, you know, a video game.
As someone who played them both in their time, I don't even bother trying to compare which was better. I don't think 7 was leaps and bounds above 6, but neither do I think it was a cheap knock off that was more flash than substance.
I won't get into the technological improvements at all, because that's very much up to the individual, though I would say the "visualization" of the Midgar slums pales in comparison to the choice of music, especially compared to Zozo. The themes used in Midgar had a feeling of foreboding and deep sadness that Zozo and Narshe simply didn't have, in large part due to the fact that they weren't the same. Zozo was mostly a joke town, after all, where everyone spoke in lies except for the one guy who said "It's dangerous here."
As for death, Tellah actually beat Aerith to it a long time ago, but that's not important. Aerith's death has never been special because it was the first, it was special because it was one of the first (scripted) deaths that properly dealt with the loss. When your characters died in FFII, it didn't really matter, because we all knew who was permanent when we picked out names at the beginning of the game. We all knew it was Firion, Guy, Maria and Leon for the endgame, and anyone else was temporary. When Tella died in FFIV, he had already gone past the point of being useful, and was more of a hindrance than anything else. I'd actually argue that point was reached the moment Palom & Porom joined the party, but I digress. When Galuf died, we felt that sense of loss for a brief moment as we remembered how much time and energy we spent on him, training him in various jobs, etc. Then...God, what's her name now? Cara? Krile? Is it back to Kururu? Anyway, she came along and absorbed all the work we'd already done with him and it was back to status quo, just with a female instead of a male.
But when Aerith died? I'd argue most players didn't even realize she could get up to her L4 Limit Break, let alone tried to obtain it. Most of the best stuff for her(the Umbrella, the Great Gospel, etc.) were likely obtained either post-mortum, or right after she left the party. Her passing left a huge gaping hole in the party, and it was felt in the story, even up to the ending.
As for gameplay, I actually would be more likely to give the nod to FFVI than VII, though they both mark a turning point in the series that I absolutely loathed. With FFVI, any character could learn any spell, so the only things that really differentiated them were the weapons they equipped, their special skills(Steal, Bushido, etc.) and the exceedingly rare desperation attack. With FFVII, though, there were only weapons, which were mostly irrelevent aside from appearance(any weapon Cloud got had an equivalent with pretty much the same abilities and Materia slots as everyone else) and their Limit Breaks. Aside from those, every character was essentially the same from a gameplay standpoint. If you swapped out Party A for Party B, you just had to switch their Materia and everything was fine. It felt cheap, and uninteresting compared to the Magicite System, which not only taught characters spells permanently, but also adjusted their stat growth, changing how they performed in combat permanently.
And, now I go back to lurking....
(I love almost every Final Fantasy before XII)