Another Man's Half-Assed View
Pre-FF1:
-Monsters take over the world (sent as punishment for people's sins by the gods)
-Magic is created by the various gods of the world and given to a select few people to help stop these monsters, and the gods have an entertaining time watching them try to control it.
-Magic is taught to those who want to be taught, and is seperated into White and Black Magic.
Pre FF2:
-Magic is written into Tomes, and given to shopkeepers around the world for the use of the general public.
-Ultima magic is hidden, as too many people have abused its power and killed themselves in the process of using it.
Pre FF3:
-Monsters sent by the gods of the world are sent to Earth to aid particular people, under the name "Espers", or "Summons".
-A law is passed that the general public can no longer use magic... only people with particular "jobs" can use them.
Pre FF9:
-Espers are renamed Eidolons, and the job system is reinforced, so now only specific people can use magic.
-The town of Black Mages is built (probably built over the remains of FF2's magic town, Mysidia).
Pre FF4:
-The gods give specific people the talent to learn new spells as they gain experience, with the exception of Summons which are forced into their own land and will not aid anybody until a person from the town of Mist defeats them.
Pre FF5:
-Because magic is getting too commonplace, the "job" system is reinforced yet again and people have to pay money to learn spells, but cannot use the spell unless they have that job or have mastered that job.
-Some spells are given a new name, such as "Time Magic", "Red Magic", and all-new "Blue Magic".
Pre-FF12:
-New Espers are created, and the others go into hiding.
-Licences are created.
-Magic once again has to be bought in order to be used, and a person must have a licence to use it.
Pre-FF11
-The job system returns.
-New races exist.
Pre FF8:
-Planet now comprised of certain alien races, older races die off with the exception of humans.
-Espers are rediscovered and renamed "Guardian Forces".
-Junctioning system is established. Some GFs remain to be discovered by man later, and Ramuh, the leader of the GFs, is never found until the next FF era.
Pre FF6:
-Espers are given Magicite form when they die.
-Magic is given to Espers, who are the only ones that can teach magic, except for those that have been infused with stolen magic.
-War of the Magi occurs, and Espers flee to their own world.
Pre FF10:
-Espers are called Aeons and exist due to the Fayth or rather, the spirits of the deceased.
-The job system exists here.
Pre FF7:
-Espers give up their magical rights, and some give magical ability only to the Cetra (Ancients). The rest let their magic flow out of them- and their spirits, too- and form Mako, which eventually crystalizes and hardens to form Materia. Espers, now called Summons, lose their Magicite form
-Humans learn how to use magic from Materia.