As the only person who likes Symphonia I just gotta say this: EGGS!
Ok let's go in order shall we?
Phantasia: It's good but that's about it. The combat is constantly moving you back and forth every swing which get's on my nerves. Oh and the encounter rate is high and the puzzles are annoying with all the enemy encounters.
Destiny (Not the remake): Boy is this one boring. It also features party members that never fight. Your basically doing all the "hard work". But it doesn't matter because the game is crazy easy.
Eternia: It's decent and one of the more challenging game in the series. The combat is a little to slippery for my tastes, though. Not much else to say.
Symphonia: It had a great battle system, so good that i ignored the shit story. It also had some non-linearity in it and alot of features that made the second play through worth it.
Legendia: Good story, average combat. Actually the combat was basically like Phantasia's (just slower) but with no crappy semi-auto combat. But some boss battles last for way too long. Oh yeah, the second part of the game should not be touched until a year of beating the first part.
Abyss: Pretty good, had potential and it had it's moments. But the characters are so damn annoying and there's countless backtracking and lack of enemy variety. Not to mention you fight the same bosses over and over again. The last boss sucks too. And it was way too long.