I'm not saying Saga Frontier is necessarily bad.. but out of everything listed that certainly WOULD NOT be my first pick.... or 2nd or 3rd for that matter.... though I will say I adored the art direction.....
how are wild arms 1+2? another long running series i have not played yet
I was in the same boat as you not too long ago, having let this series slip past me... let me tell you what, although these titles foster some acclaim, I don't feel they get near enough.. They are familiar enough as JRPGs to scratch that "classic" itch with enough originality by way of the puzzles and dungeons to really keep you going. After playing game after game after game, you start to feel as though you know what your in for and always challenged in the same ways over and over again.... As such, Wild Arms came into my life and was a total refresher reminding me great gameplay and design coupled with a decent (although not stellar narrative) equates to a freakin' great game that doesn't have to go out into left field to feel like a very original experience.
My advice though, if you haven't played all this stuff listed here is to go for the Suikoden series. Suikoden 1 was a bit unbalanced in the sense that with the right characters in your party, the game can prove ridiculously easy.... But half the fun for me was discovering those character combos that really let me stick it to the enemies. The narrative sets up for Suikoden 2 beautifully and makes that experience all the better. Without getting into anything else, on all RPG fronts I found Suikoden to totally rise above mediocrity and enter the realm of completely awesome in many respects. It is original, has a great narrative and soundtrack, a wonderful cast and just too many good points to be a "bad" or "mediocre" game... In other words with suikoden 1 and 2 is VERY safe to say you won't regret your experience.....
.... Now in a completely subjective sense, I would definately second the Breath of Fire suggestions that have been presented here as well... I am probably the only one who liked 3 more then 4 but both were great to me and well worth playing. In any event, its just plain-jane solid JRPG goodness here..... But I am a Breath of Fire whore and loved the first 2 which many people did not so I could be bias, which is why my first suggestion to you is Suikoden or Wild Arms if thats seems more appealing to you.
After those I would head into Xeno, Star Ocean 2, Grandia and Valkyrie Profile. Those three are all really great titles but each are great for their originality in different respects that place them sort of outside the realm of your standard stuff.
Lastly, I want to mention "Thousand Arms" as my obscure title suggestion to look into for the future.... I know not many people talk much about it or like it.... and I myself don't have enough experience with it to say either way yet, though it is sitting on my shelf beggin for a play-through. But it looked interesting enough in a real odd-ball sense to catch my attention..... In fact, if anyone here has experience with it, I myself would love to hear it.
EDIT: I made a boo-boo and wasn't mindful of what it was you orderred already. Plus completely neglected to mention in my top suggestions.... Lunar 1 and 2 are quite possibly my favorite PS1 RPG's period. But they are not for everyone.... They are very straightforward and typical, but also very well done. I would actually place the Lunar suggestion above my others if you are looking for a very "standard" experience and classic fantasy narrative that is well told enough to keep you hooked.