Star Ocean 1: Solid, with various aspects revolutionary for its time. Full 3D plain real time combat, optional after game dungeon/super boss, item crafting etc. Only reason this game doesn't get more attention is it wasn't localized on the SNES.
Star Ocean 2: Improved and expanded on many aspects from the first as well as added more very unique elements to the RPG formula, some that still stand up today as one of a kind. For that reason this is one of the best JRPGs of all time.
PSP port version was worse though, for instance, they made the main female protaganist look 8 when in the original she looked like a regular young adult. Guess that has to do with the pre-puberty fetish Japan seems to have now. More evidence that this is a new trend.
Star Ocean 3: Took a few steps back from SO2. It did improve upon some things but overall this game was far worse. Even so I would rate this higher than SO1 BUT the ending killed it. One of the worst endings in any JRPG ever. It was so cheezy it would make Nintendo cringe.
Star Ocean 4: Have not played but based on fan opinions, this one was several steps back in just about every area. Especially regarding the story and characters. More kid fetish stuff apparently and cornyness. Japan really needs to get over these terrible trends ruining great series.
I didn't like how being knocked down to 0 MP in SO3 would KO a char. I think there's a reason why that mechanic is seldom used..
Well it was an interesting idea and didn't take anything away from the gameplay but I agree it seemed kind of pointless because I heard most of the time HP kills were still the fastest and best method anyway.
The original Star Ocean was decent; pretty archaic but not a bad game. I played the PSP remake. There were a few things I didn't like compared to SO3's combat, though.
I only played a bit of SO2 on the PSP remake and it just didn't really catch my attention; not that it was a bad game or anything.
Gameplay of SO3 is one of the best. So many strategies and ways you can play the game, and it made doing low-level challenges possible. Obviously the story was not amazing, but it wasn't that bad either.
SO4 was decent, but not really as good as SO3's combat. There were some neat tricks and things to do, though. The characters were pretty meh, though. Story was mediocre.