I actually enjoyed 8, especially once I understood the way the leveling and drop system worked. The spell/stat joining was pretty neat. The story was good in places, horrible in others. 9 was just awesome. Here's what I've played, more or less:
1 - Awesome Classic
Mystic Quest - Why, Squaresoft, why?
4 - I <3 Dragoons
5 - Awesome Character System
6 - I've only ever gotten like halfway through, graphics were pretty cool, story was interesting, but just couldn't keep at it
7 - I go OCD when playing this one, love it.
8 - See beginning of post
9 - DRAGOONS!
10 - Meg Ryan in the best interactive movie ever
10.2 - Fan Service, some of the system was...interesting, but the story in what I played of it was preeeeety ghetto
12 - Still have a ways to go in it, but it's been enjoyable, decent story, fun battles
Tactics - I go OCD when playing this one, love it!
Tactics Advanced - A let down compared to Tactics, but still fun