I voted VI because it's my favourite, but really any game pre-VII was pretty clear about what was going on all of the time. Probably in part due to the fact that the space on the cartridges was so limited that it made sure they kept things clear and to the point a lot of the time. I mean you can sum up the overall story of FFVI as FFVI spoilerevil empire using magic to take over the world. Fight evil empire. Kefka destroys the world. Fight Kefka. Mind you the straight forward nature of the overall plot isn't all that made it clear. It also helped that what you were doing and where you were going typically had a clearly explained purpose that made sense in the context of the story.