IV's gameplay can be described as rather 'thin' compared to other entries. But the same could be said of the first game, the seventh game, and the tenth. Seeing a pattern?

They were all the first game on that system...there's always an adjustment period with new hardware, or so I am inclined to think.

V's Job system is superior to VI's esper system. I'd grant that. But what it has in terms of gameplay it seems to sacrifice in storytelling. I never cared for the story and no argument for it has ever seemed compelling to me. It comes off as a low-calorie version of a usual FF story.