A further thought occurred to me over the past week and I thought I'd add it as an addendum to my previous post. I noticed that the plot felt "tighter" in the more constrained first third of the game. The slums under Midgar are constrained in space, atmosphere, tone, action, and cast. It is a wonderful feeling when you finally get out of Midgar and find a whole world to explore. That said, after a half-hour or so of play it becomes clear that this new world is far more diffuse. The cast begins to widen out beyond what the story is able to fully develop. The action for many hours consists of chasing Sephiroth to a series of new locations that are only visited once or twice and these new locations lack the deep and consistent atmosphere of Midgar. All these changes alter the tone of the story in ways that can be jarring. The "tightness" wasn't there any more.
Thinking about this reminds me of G.K. Chesterton's aphorism: "art is limitation." In other words, meaning requires form and form means setting limits. The picture shall go this far and no further. The sculpture shall be of these materials and not those. This is a challenge for any epic fantasy game. "Epic-ness" requires all the vastness of a real world. To make that world cohere as an artistic whole requires unity and detail. The two goals pull against each other. Perhaps game design has grown enough with the advent of the MMORPG to resolve this tension. If so, then it's a real creative break-through. It also means that even Final Fantasy VII's artistic failures were productive in the long run.