Okay so I've never played any of the FF games, so sorry for asking, but what makes this particular FF worth remaking before any of the others? It looks really cool from the trailer, I'd be interested in learning more about it.
Final Fantasy VII is by far the most popular. VII, VIII, and IX were Sakaguchi and Uematsu's apex. When Enix bought Square, X started the decline, and they both left after that. IMO the new games are alright, but they're not 'Final Fantasy' good. RPG are about the story, and FFVII is just a really great story. I mean, I could tell you the story, but I'd hate to ruin it for you. Incidentally, Sakaguchi (the designer) and Uematsu (the composer) now have their own company, Mistwalker, and they're making some really good stuff. Like The Last Story that I mentioned. Also, Nobuo Uematsu's music is independently phenomenal.
I think it's also important to remember that FFVII was the first 3D Final Fantasy and possibly even the first decent 3D RPG. FFVI is one of the most memorable games I've ever played but it doesn't get nearly the attention that FFVII does. And isn't this the second remake?
I should add, IX is my favorite. It's a return to the classes from the old 2D games, and a really good fantasy story (whereas VII and VIII were more technological). And VIII is often considered the best Final Fantasy love story. Also, a warning: if you play VIII, do not power level. The higher your level, the harder it gets. It's broken. Just play thru without grinding and you'll be fine.