Yeah I've heard good things about the JP only ones on PS2. Don't have an easy way to play them without pirating though.
Symphonia is a pretty good game, maybe a bit kiddy but a pretty fun game. I'd say overall it's worth playing even if that's a turn off.
Eternia was a fine game for its time, it feels like most tales games.
I felt the GBA port of Phantasia was decent, I haven't played the really old ones.
I don't rate the series that highly for the most part. The only one I'd even rate with other JRPGs is Vesperia. I dislike a lot of the traps the games fall into. Still, they are decent enough to play and have for collection purposes.