>>714814307FF1 - the most limited in what you can do in combat.
FF2 - offers some more combat options, plus lets you build your characters however you want (there are no jobs, just skill levels)
FF3 - has the first iteration of the job system and you can change jobs out of combat depending on what you want to do.
FF4 - ditched the job swapping and just made every character a different job, but there is also a lot more going on mechanically with each job and fights
FF5 is the superior job system, allowing you to pick which jobs to use and, as you master them, you can then assign skills you've learned to other jobs and get creative with combinations.
FF6 - similar to how FF4 functioned, but with the addition of magicite that lets every character learn magic in whatever order you choose.
FF7 - all characters are functionally the same and the only main difference being their limit breaks and what weapon they can use.