FFI has two (PS1, GBA), FFII has one, (GBA), FFIII has one (DS), FFIV we covered already, FFV has one (GBA), FFVI has one (GBA), and FFVII has one, (PS4). They probably won’t make another one.
FFI II received a Wonderswan Colour remake, which is what the PS1 versions are based on. The GBA remakes retained the graphical style but added new content and changed the mechanics to bring it line with systems introduced in later games. I and II were then remade for the PSP, updating the graphics again and introducing even more new content, which then were used for the mobile ports.
The III remake on DS was also ported and enhanced on mobile, PSP, PC and Ouya (lol).
FFIV is interesting since it has a 2D GBA remake, which then got remade in the same style as I and II for the PSP but it also has the 3D DS remake, which was then again enhanced for mobile platforms.
FFV has the GBA remake, which was then remade with a **** art style for mobile and PC.
FFVI got the similar treatment to V, having a GBA version with additional content but then was completely ruined in the mobile remake.
VII's remake is more or less a reboot. You also have the modern console ports with slightly improved models, controls and quality of life options.
VIII got shoddy steam port that added the Pocketstation features for the first time in the West. It was then "Remastered" with quality of life options and upgraded character models.
IX has so far not had any remakes aside from modern ports with quality of life options.
X received a HD Remaster for the PS3, making the game widescreen, remixing most tracks and updating models and UI all over the game. The HD version was then ported to PS4 and other consoles.
I could go on about all the different ports and version differences but I should get back to work.
