Well, Star Ocean 2 will always have a special place in my heart. It was so innovative for the time, even if it was somewhat cheesy. Star Ocean 3 was worse, much worse, but it did have some redeeming qualities. While the storyline itself went off of the deep end near the end of the game, the back story and Sci-Fi elements -including false scientific advancement like Graviton Warp- were all pretty well thought-out. The battle system would be beaten by more fluid real time RPG action later in the days of the PS2, but it is still decent and fun to play. The dissapointing end to the game and its silly grinding/item creation were its real draw backs.
And yes, Star Ocean 4 was clearly terrible. The battle system could not even live up to Star Ocean 3. To be honest, despite how much I love the series, I could not get very far, as I gave up in disgust.
Tri-Ace seems to be suffering from the same problems that other SquareEnix developers are. These problems are too many to list here, but with the obvious decline of Star Ocean and Final Fantasy, I would not hold your breath for any worthy sequel to emerge.
Ominous Latinus Phraseus