I be honest. I just can't get into anything past SO2 series. After that uptil Blue Burst, it all wented down hill. Just like Final Fantasy X and up, their are too many stereotypes. FFX-X2, just had too many stereotypes, until FFXII where it final just decided to be DADish.
I like how the kept the Underworld/Demon King/Goblin King/Gaberial/Satan/etc ( the inorganic made one ) in the whole series as the underlining foe. The mutants, and artificially created magical beings.
Speaking of Blue Burst, which pretty much has an end Senario as with Phantasy Star II ( you fight an alternative version of yourself in the end ). So it is pretty much inevitable.