It will be kind of hard to determine which games are the middle of the road, so I will be separating the games I think are genuinely good games, and which games are just okay. I don't think any Final Fantasy game is actually poor but there are a couple that are on the bottom for sure. I won't be getting into sequels and spin-offs, or online games. OST means original soundtrack when I use it.
First of all, this is the list of Final Fantasy games that I think are good games:
Final Fantasy X
Final Fantasy IX
Final Fantasy VII
Final Fantasy XIII
Final Fantasy VI
Final Fantasy IV
VIII and XII
Lets go over the Just Okay games.
I and II - offer nothing to someone who didn't own them on NES, because their only selling point is nostalgia and catchy 8-bit music. There is much better nostalgia and much better music in subsequent releases. And honestly there are only a couple non-mario NES games worth playing in 2018 anyway.
III - I tried this game on DS and I just couldn't get into it. It lacks the flare and intrigue of IV, which is also on DS, has some dull protagonists, and since the DS graphics were one of the things i didn't like about IV, they certainly weren't going to help me admire III. The soundtrack is also too much like I and II.
XV - The game's opening, pushing a car that won't start, basically summarizes how I feel about this game. It's a monotonous crawl where Noctis is the only interesting character and even he and his Sasuke-rip-off boyish charm can't save this game from falling flat on it's face. There are better open world games out there. There are better Final Fantasy games out there. And I think the combat looks silly. This game is Squarely (see what I did there) at the bottom of my list because at least the other games in my Just Ok list are actual Final fantasy games.
TL;DR: I don't like this direction if the franchise is going to continue this way.
V - Probably the game with the most potential of my Just Okay titles. I think terrible lines and localization are the main problem. The job system is interesting and some moments are quite amusing. The game looks like absolute shit visually, even for a snes game. This and VI could certainly benefit from the DS treatment III and IV got, and on 3DS they would look even better. It's too bad it probably won't happen.
Middle of the Road:
XII - I think 12 is actually a good game. It's fun, addictive, and makes grinding enjoyable somehow. Balthier is one of the best characters Square has ever put out, and I love some of his one liners. I don't think XII is a good FINAL FANTASY game. It goes off too far from it's roots and feels like it's own thing. I think I'd respect square a little more if they just gave it a different name and released it as it's own IP. This is one I have no problem going back because it has a lot of charm and replayability.
VIII - I have a love hate relationship with this game. It's the first Final fantasy game I ever played and it set the standard for me. It has the best soundtrack of the entire franchise. It's quite possibly the best OST music on PS1. It's clearly Nobuo at his absolute apex. You hear a little bit of his apex in VII and IX as well, but because VIII lands right in the middle it's the golden goose of Final Fantasy OST.
I like Seifer, Edea, and Ultimecia as Villains - I enjoyed Sacred and Minotaur's back and fourth while you battle them. I even like Raijin and Fujin's squabbling. In fact most of the protagonist characters do interesting things. But the actual plot is a clusterfuck. The scene at Trabia garden makes me want to slit my wrists in boredom every time. The game basically doesn't have a plot and it tries to pass that off with time-loop, paradox bullshit, and things were going so well up until I'd say about end of disk 2. Edea should have continued to be the main villain and Ultimecia should have been like the Sith Lord Sorceress who trained her. The game's plot is about a 6/10 before it blows up, and a 0/10 after that, and the scene at Trabia is about a -2/10 because it's so long and awful. I hate that light house. So I like most of the characters and I hate the world they're in.
The draw/junction system is a terrible idea and easy to game the system. Playing hours of cards so that you CAN game the syustem is a long tedious monotonous chore but at least the card game has really good catchy music.
The gameplay in battle (and the music really helps this) is catchy, addictive, and endearingly awesome. But it is marred by the fact that the draw system is there, and you can make yourself overpowered at level 7 if you want. Infact, leveling yourself up makes the game harder which is dumb.
The Music gets an 11/10 from me.
The characters including Squall get a 9/10 from me. I didn't particularly like Quistis.
The story gets a 2/10 - with squall is dead theory bounce that up to 4/10
The world gets a 4/10
The battling gets a 7/10
Minigames get a 7/10
Replayability is a 6/10
And overall I give the game a 7/10.
Good Final Fantasy Games:
Final Fantasy X
This game is really easy unless you choose to make it difficult. It has a couple of places where the voice acting is pretty bad. The Final Boss literally can't kill you. Those are my only gripes with it.
Final Fantasy X has some really excellent voice acting and character building for both it's protagonists and villains (Seymour and Yunalesca), and some of the most emotional speeches in Final Fantasy. It has my personal favorite character, Rikku, and it brings the steal/use and mix systems which are inventive and add a lot of depth if you opt to:
Make the game harder by Not using Yuna, Play a No Sphere Grid Challenge, or play as ONLY Rikku.
Even if you hate the game's story it can be a fun challenging experience to play without using Yuna. I personally like the story and world building. It's replayability does go down over time though. But it has more replayability than a game like VIII because if you beat the game using just Rikku you can play it again and try to beat it using only Wakka who plays completely differently.
Final Fantasy X's easy difficulty is secretly it's biggest strength.
First Play Through: 10/10 (or X/X if you prefer)
Subsequent Playthroughs 8/10 with a .5 taken off of each playthrough.
Music: 10/10 - Not quite as good at VIII's.
Voice Acting: Varies but more is good than bad.
World Building 9/10
If you hate this game please try playing it with No Sphere Grid.
Final Fantasy VI
I've never gotten very far in this game because I am not sure how to get last the part where you're drifting down the river and that one boss keeps OHKOing me. I refuse to look up a solution and instead I just put the game on the back burner.
However the beginning of the game showcases the wonderful characters, music, and world building enough and I trust others that this game is probably objectively the best title in the series.
Final Fantasy VII
Probably the best world-building in the franchise, certainly the most interesting main protagonist. Cloud is Cooler than Squall, Zidane, and Tidus. I didn't even find him too edgy or emo. I think he has just enough edge to have bite and attitude but not so much that he drowns you in it. He simply doesn't care and he wants to get paid. He's a relatable protagonist even though he's an experienced super soldier.
The fighting theme for normal battles, and the victory fanfare I think are the best in the series. Even if FFVII was a terrible game with a plot shittier than VIII's that battle theme could carry it on it's back. It's Just. That. Good.
I don't think anyone needs Convincnf that FFVII is a good game or has the most nostagia value per capita of any of them. There is a reason why square is willing to spend millions to redo it with modern graphics and a new battle system.
And because there isn't really overpowered summons available early on, I feel the combat has more depth and strategy involved than IX, VIII, and certainly X. Final Fantasy VII's one legacy blemish is that it looks like ass nowadays. You could argue it looked like ass even when it first came out. Other than that it's probably a perfect game. Certainly a 9/10.
Final Fantasy IX
This game goes back to the roots of the franchise, and yet it's also the most unique game in the series because of it's art style, moralistic themes, and interesting world and characters. I am only about half way through it so I will finish this part later.
Final Hallway 13
Okay, yeah it's lack of directional options and rail road plot are limiting. But it's hard to deny how pretty the game is or how excellent the cinematics and music hold up even today. XIII is probably the most stylish and best-looking and sounding game on 360/PS3. Square held nothing back. It sold better than 123 and X and spawned two sequels. The first of which was pretty good and the second was wtf.
It's not the best game in the series but it's a good return to form after what we got from 12. At least it tries to be Final Fantasy.
Final Fantasy IV
It's just a good game. Will add more to this later.