I've been continuing my quest through the series, but haven't bother posting in the thread about it. Just finished up 9 and I figured I'd write a few sentenced on each game so far. As always, I played the original versions on actual hardware.
4: I really like the chapter system, playing as a merchant in chapter 3 was pretty fun. The fact that even people not in the active part would get experience when the wagon was there was a huge QoL feature and quite a head of its time for a game this old.
5: Probably the best story of the bunch, though I did find each sections story was worse than the one before it. Playing not as the hero, but the hero's father was a fun twist though. I did not care for the monster taming and mostly stuck with the human party members when possible. .
6: A huge world to explore, especially after beating the first demon lord and getting the ship. The vocation system makes a return and is a strict improvement over 3, though it is grindy and the hidden level caps are annoying. I wish every character at least started with a vocation, then you get to unlock changed them later.
7: Long. Probably could have been 20 hours shorter. I do see why they are removing some of the islands in the remake. Plays more like a series of short stories, and they vary a bit in quality. Favorites were Falrish, Dialac, and Dharma temple. Vocation system returns from 6 and is pretty similar. Still really grindy and it isn't helped by party members coming and going and having to catch them up when they return.
8: This might be my least favorite. The story really didn't do it for me, what with always being one step behind and I felt like the characters just stood around like retards a lot of the time. (Like when both Sir Leopold and Marcello pick of the staff). Gameplay was fine, though it was annoying that you kind of have to place skill points blindly. The final boss was also not very fun. Having to pray with all 4 characters 7 separate times before you can damage Rhapthorne wasn't hard, just tedious.
9: Gameplay wise, probably my favorite, combines the vocation system with the skill points from 8 (but at least shows you what you get at each threshold). Story was fine, but nothing to write home about. While I don't have any plans to do any of it, there is a ton of optional post game content if you are into that sort of thing. Probably the game most in need of a re-release of some form as it's stuck on the DS.
Will probably take a break and play something else before starting with 11.