Final Fantasy IX
Yeah, there's Final Fantasy VII and Final Fantasy VIII, Legend of Dragoon and Suikoden, Chrono Cross and Xenogears, Valkyrie Profile and Vagrant Story...
But of all those titles (and yes, before you bash on me, I've played them all) Final Fantasy IX definitely had the most epic environments. The castle within a city within a fortress Lindblum? Imagine that one all built up out of polygons. The unbelievably gigantic tree infested with zombies (and zombie dragons!) known as the Lifa Tree? Yeah, I'd pay to see that one in HD glory.
Burmecia, the realm of eternal rain;
Cleyra the nation residing entirely inside the top of a tree surrounded by a sandy vortex;
The unworldly Terra;
The upside down Ipsen's Castle.
In the end, tho only new thing a remake true to its roots has to offer, are better graphics (and in this case, voice-overs). So yeah, I'd go for the one that is visually most interesting.