Okay, so now that I've calmed down from the initial hype and have some time to really think about how I feel about the remake, this is what's on my mind: I really hope Square doesn't overthink this.
What I mean is that I hope they update what needs updating and leave what's fine alone. The actual core game play of FFVII, the battles, the materia, the countless goofy mini games, are all still pretty fun and engaging even twenty years later. Since all we have is a pretty CG teaser to drum up some hype there's no real details here. They could go either way with this one, but the very nature of the project is risky. If they chose to only tweak the game play then there's going to be a notable amount of people who consider that "lazy" or who find turn based JRPG game play boring since it's appeal isn't nearly as wide anymore. On the offhand, if they completely revamp the game play into a completely different beast then the countless people who had fond memories of the original are going to be disappointed.
Personally, I would rather they just tweak the game play and stay away from trying something new and wild with it as they've been doing with the series since the early 2000s. As I said, the game play isn't broke, so it doesn't really need fixing.
Then we get to the story.
Obviously there's going to be a few changes here. The real question here is how closely does Square want the remake to feel to the Compilation? At bare minimum there will be small changes made here and there to make the spin-offs tie into the original a bit better. At the same time, how close will it be to the original? The changes made to the characters and universe as a whole in Advent Children are already pretty divisive, so no matter what they do once again not everyone is going to be satisfied. FFVII has been molded by Square in the spin offs to be some kind of somber, emotional epic. But the original game was anything but. What is Square going to do about the parts that don't fit this vision of what FFVII is? Are we going to have to cross dress to save Tifa again? What about the magical legless floating old man who is
very important to the story but is never mentioned in the spin-offs? Will Cid ask us to drink our goddamn tea? What's going to happen to the goofier parts of FFVII?
And that's not even hitting characterization changes. In the original game the Turks were cold, cunning, ruthless monsters who were absolutely loyal to the very evil Shinra (or Shin-Ra since we're getting all nostalgic here). The spin-offs turn them into a group of goofy, bumbling comic relief. Try watching any funny or charming Turk scene from Advent Children with the fact that these people are directly responsible for the murder of at least a million people.
So yeah, my biggest fear is that they'll try to turn FFVII into something it isn't. Chances are this will be the case, but I'm cautiously optimistic at this point.
EDIT:
Also, here's the trailer for anyone who hasn't seen it yet.
