I originally thought that maybe they weren't being that ambitious, just updating graphics and trading on the original popularity of 7 etc, but I'm coming to realise that the scope and dedication to this cause is staggering (no pun intended). The original followed much the same path. Linear Midgar, becoming more and more open as the game progressed.
The sophistication of recent FF games, current hardware, and storytelling/world building from earlier games in the series, it's a fantastic recipe.