Mileage varies, of course... I didn't like 8 because none of the characters were all that likable, but every other game they've done I've enjoyed. 12, my only real complaint was the whiny teen hero. 13 was good, pretty much what I expected, though it could have cut down on the opening cinematics and guided gameplay.
That's something they need to cut down on in general. They need to allow us to get IN to the game faster and actually start doing things. Cut down on the cutscenes, get us interacting with the characters asap. But other than that, I enjoyed the story and the look and feel of the game.
11, I played that at release, and I still play it today. They've put a lot of work into that game and they're continuing to revamp it. I'd say it's better than ever now.
14 was very pretty, but suffered with a clunky, laggy interface. I haven't played it enough to really get into the story, but so far it seems pretty engaging. I think they were pushed to release that game WAY too early, it's still in beta phase. They're listening to customer feedback, though, and I think they'll make good changes to it. In a few months, it will be a game worth playing.
So, my advice to SE:
Stop with the Whiny Teen Hero. Angst is good for characters only when they have a REASON to be angsty, and only when it moves the plot along
Cut down on the cutscenes. Those are the most expensive parts of the game anyway. Short, occasional cutscenes can enhance a game, but longer ones detract from gameplay by basically taking control away from the player. If I wanted to watch a CGI FF movie, I'd just pop in Advent Children again.
Do more to connect the player to the character. We need to empathize with the characters we play, we need to like them, and we need to feel like we're sharing the adventure.