Since I never played FVII - is it really that huge? Or are the others (8,9 etc) bigger (which I assume)?
Weird that they chose exactly that title to make a comparison. Or maybe because they assume fans like it the most? (not saying that they do though lol)
I'd say, in overall scope, FFVII IS pretty big. Probably not the LARGEST FF(I think FFIII-V are the largest adventures, if we are talking about the exploration of "more than one WORLD"), but still considerably great size. I think it's probably one of the last "classic FFs" in that regards. It's even the last FF where you can explore the oceans in a submarine(which underwater exploration occurs in it's own "undersea world map").
But as far as the context of the PR person, I think, like others have said, they mean "popularity". And funny thing, the folks at Square Enix once said that when they make a game that surpasses FFVII's quality and popularity(keep in mind, FFXIII, to them, wasn't it), THEN they said they'll remake FFVII. Not saying it's a sure thing, but if FFXV is a hit, we might see something drip down from the Mako reactor!