Star Ocean 1 is basic RPG. It's fun but by the time we actually got to play it via translations it was kinda meh.
Star Ocean 2 was great. Fun, good story, good characters, reasons to play though it multiple times. The only real bright spot in the series. At it's release it kinda stood out with Private Actions and the crafting system from the other JRPGs out there.
Star Ocean 3 is a mixed bag. The original SO3 was horrible, don't forget we got an updated director's cut version of the original game becasue of all the missing content in the original JP release. Outside of the cool plot twist the game is mostly forgettable and takes a shit all over Star Ocean 2's plot.
4 was boring all around outside of battles when using blindsides. But even that got boring quickly. It tried so hard to shoe-horn itself as the beginning of the series plot-wise and it just didn't work out.
I want to play 5 but I know I'll just be disappointed. Maybe we'll get another directors cut version of the game with fixes. But I doubt it.