Since you're a big Nippon Ichi fan, I recommend
Chaos Wars, which is not by them but is very, very clearly inspired by their style and shares their sense of humor. It's a massive strategy-RPG crossover between characters from different RPGs... you don't have to know all the various games they're from, but if you're going to play Growlancer or Shadow Hearts, play those first so you'll recognize the characters when they appear in Chaos Wars. Oh, or Gungrave. Or the Shinsengumi (yes, really.) It is rather hilarious having
Soji Okita, Princess Anastasia (the Shadow Hearts version), and Grave from Gungrave beat up on an enemy from a random JRPG.
Of course, if you just want RPGs, the Growlancer series isn't bad, and the Shadow Hearts series is very good. And, um, did you leave Suikoden off by accident? Suikoden III and IV weren't as good as the rest of the series (play I and II for the PSX if you haven't), but Suikoden V is quite good. You might also like Ar Tonelico...