I see what you're saying. FFVII was leitmotifarific. Some of the greatest character-to-song connections were made in that game and OST. And that is certainly one of the marks of a good soundtrack.

I disagree, though, that IXs music isn't as memorable. For that matter, the VIII songs that you mentioned aren't the ones that stood out to me: Balamb Garden totally sticks, as does Man With the Machine Gun (even though the latter is an example of music not "fitting" the moment, at least for me). And I would suggest that if you asked the average FFVII player, they wouldn't remember as many songs outside of the big 2 or 3 as you imply.

Also, I didn't say FFVI's soundtrack wasn't cohesive. It's one of the first games that ever made me think of video game music on the same level as say a movie score. One of the first games to truly make me realize that games could be art. It's just that Uematsu got better at it in later games and by FFIX, he'd mastered the form, or at least his version of it.