FF 1 and 2 are trash, IMO - too old school grind heavy for me
FF 3 is good, but avoid the DS/iOS versions - the 3D remake has a super slow slow battle system and the game is grind hell - so be prepared to wait a lot as you press the action button over and over and over and over and over again. No real story to write home about.
FF 4 is good - Even the 3D version is good for this one
FF 5 has one of my favorite level up systems in the series which is a more refined take on the same system as FF3.
FF 6 is is pretty good but is not the end all be all game that some people make it out to be. Has some interesting gimmicks with the battle system, and is the start of FF games having carefully plotted and frequent story moments. The music is fuzzy low quality SNES standard fare, though some of the compositions are pretty good.
FF 7 is okay I guess. It has some pretty creative concepts but that all goes out the window whenever they start hammering on that metaphysical bullshit. Boring but non-offensive battle system. More crappy quality but sometimes well written MIDI music.
FF 8 has a more engaging battle system than previous FFs, does not require grinding, and has a completely new and pretty awesome character advancement system. I know what you're thinking: this game must be awesome. Shame about the game having the worst characters, world, and story in the entire series.
FF 9 is a semi-throwback FF. Sometimes funny, very slow battle system. I liked it
FF 10 is divisive. I liked this one. I liked the level up system and the end game content. Has the best song in the series
FF 10-2 is a game where you play as a bunch of 16 year old girls dressed in slutty outfits. You also listen to a lot of shitty j pop and elevator music. The cutscenes have upskirt shots for every voiced female character in the game. Be prepared to watch a lot of 7 polygon crotches with 5x5 resolution textures in this "girl power" FF game.
FF 11 is an old pre-WoW MMO in the gameplay vein of everquest. I had fun with it. It punished bad players as well as those that played with bad players. I heard it is now gimped to the point where you can reach max level in a manner of hours now.
FF 12 is a fun game with a completely different gameplay style than other FFs. I loved the presentation and playing the real time combat on near the highest speed with the option to pause the game in combat disabled. Gameplay can be made trivialized by abusing the game's AI scripting.
FF 13 is a now gen FF game with good graphics, a good battle system, and not much else. Has the most annoying character in jRPG history and has the most annoying Anime trope that made me stop watching anime. I still beat the game with these problems because it is fun to play.
FF 14 is a mess. Fuck that game. It's another MMO that was so fucked up that Square extended the 30-day free trial to last for over a year, fired the development team, issued 3 apology letters to the fans, the CEO of square said that the game has permanently damaged the FF brand, and they are working on a new patch that completely changes every single aspect of the game. It's a fucking lost cause.