I always think these lists are fun, even if I disagree. It's all subjective at the end of the day and gives a fun opening to talking about the series as a whole. Wrote out my own ranking, because why not. Work is slow today.
1: VI - total agreement here. It has its flaws, but I find the cast charming and the story compelling. The art direction, sprite work and music all hold up amazingly well to me. Shout out to Relm, one of the only child characters in a JRPG I actually like. I love the conceit of her being an artist and wish we saw more characters like her. The villains may be pretty one dimensional, but I kind of like that about them. They aren't overly convoluted or over/under explained. Kefka just loves being evil and I love that for him! I always have a great time coming back to this game.
2: IX - and immediately we diverge. I love 9. I think it has some of the best, most cohesive storytelling in a final fantasy game. People (rightfully) talk about what a gem Vivi is, but I think Garnet is easily one of my favourite characters in the series as well. Her wrestling with responsibility, growing up, family betrayal, falling in love is all handled really well. She's naive but not arrogant. Kind but not a pushover. Makes mistakes, but does her best to learn from them. She has strong growth throughout the story and I just love how the writers use her and Vivi to grapple with loss of innocence and the impact of time. The game definitely has flaws in the combat and some of the side characters, which pulls this game down from being number one, but I think the strength of its storytelling is just leagues ahead of most of the series. I also love the art direction, especially when it comes to the city designs. It really stands out amidst the hundreds of games I've played over the years and adds a whimsy that juxtaposes (for me) well with its darker elements.
3: VII - One of the first games I ever played. Not much to really say that hasn't been said a million times. I also really love the storytelling in this game, warts in the translation and all. The character designs and personalities are engaging and well realized, the music is top tier, and I love most of the side activities. I do knock it down a bit because the pacing has issues and some of the story aspects are hidden behind side stuff that really shouldn't be. I think my favourite stuff about the story can't be talked about without spoilers, but I think where it succeeds is much more compelling than what I think the remakes are going for. Hope to be proven wrong!
4: X - I just think it's a good ass story. The romance is actually believable, both Tidus and Yuna grow a lot as characters and I LOVE the ending. It's ridiculous at times, but all the story elements feel reasonably well realized and cohesive to me looking back on the game. I think the way it examines sports and religion is genuinely thoughtful and makes it feel unique compared to similar games. It also has some of my favourite art direction of the series. I love the locales and temples you visit. Also my second favourite summon designs next to eight. Loses points on being so linear and the side activities being actual nightmare fuel. Fuuuuuuuuck that chocobo obstacle course. Never again will I do the lightning strikes.
5: V - The most mechanically fun early final fantasy. Straightforward but engaging, love the costume designs for the jobs. Also: Faris (and the rest of the party, but mostly Faris) rules. Give me more Faris Square, you cowards!
6: VIII - I really struggled with placing this one. Controversially, perhaps, I love the gameplay mechanics. Mixing and matching spells and GF's is fun to me and the game is so easy to break that it's super replayable.The side stuff (outside chocobo forests) is great and makes the world feel worth exploring. The cast is a mixed bag, but I think Rinoa and Squall actually feel like fairly believable teenagers who develop and grow and Selphie loves trains and explosions, so yknow. There's some good to be had. It is maybe the most ridiculous story of any Final Fantasy, which I kind of love it for. But... half the cast is just deeply underdeveloped, the pacing is all over the place, and drawing magic was such a pain in the ass before they introduced 3X speed in the re-releases. So that all kind of keeps it from the top of the heap for me. To end on a high note, because I am constantly yo-yoing when I discuss this game: it has my absolute favourite soundtrack in the series and my second favourite art style next to ten. The GF designs also get special shoutout. I would kill to get doomtrain in another single player Final Fantasy.
7: VII Remake - I also struggled with where to put this. Some of the decisions they've made really don't sit well with me story wise. I won't get too into them here, because it would take forever and be largely spoilers. But the characters are really nicely realized and I LOVE the new combat system. I put it on the lower end of what I consider good because I think I still need time to decide how much the stuff I dislike impacts my feeling of the game as a whole. Soundtrack is also largely excellent, though I kind of miss how grimy feeling some of the tracks felt in the original, due to the worse audio quality on the PS1. Yes, I realize that's a weird take.
8: XII: Zodiac Edition - I love playing this game mechanically, but I could not care less about the story. It is so boring and weirdly paced, especially if you're actually doing a lot of the exploration and hunts. The characters are okay, but kind of bland. The main party also have some of the worst designs in the whole series. I hate all of them except maybe Penelo's, who I'm indifferent to. Still, there's a lot I like in the themes they were reaching for, the locales are a delight to explore and gambits are actually kind of fun to mess around with once you get used to them. This edition is also really aided by the job system, which adds depth and replayability. In contrast to later Final Fantasies, I think the Hunt system is the best it has ever been and I actually liked thinking about how to approach them. Felt like there was real depth and some good world building stories to be uncovered by engaging with them.
9: IV - Sorry FFIV lovers. I want to like this game more than I actually do. It's fine, nothing stands out to me as truly terrible or truly amazing. I like the cast, but I don't feel much attachment to them. The story and world aren't overly compelling to me. There's a couple good standout moments, but overall this is probably my least revisited of the ones I played as a kid.
10: XIV - oh boy. Okay XIV lovers, I'm sorry. I tried. I played maybe sixty hours of this game and it is just not for me. My favourite thing about it was unlocking triple triad (admittedly, I did have a ridiculous amount of fun playing triple triad). All the dungeons and story were boring to me, I didn't care for the sidequests or job quests I engaged in, and it all just sort of blurred together into a mostly bad time. It didn't help that when the dungeons finally began to get more complex, rather than braindead easy, I couldn't tell other players that I had never done them before without slowing everything to a grinding halt as I tried to type with the PS4 controller. I did have some fun with the game, and I believe people close to me who say they love where the story goes. But if I'm sixty hours in and can't remember a single character's name, I don't know why I care to see where they end up in another hundred hours of gameplay. I fully realize this seems to be a me issue, and would concede this probably belongs higher than here quality wise.
11: XVI - I do not like this game. I will refrain from digging into it since I know it's been a big hot debate topic as of late. Cid is cool though.
12: XV - I REALLY do not like this game. Do like the road trip vibes though.
13: XIII - This game almost made me stop playing Final Fantasy. I can't think of anything I like about it.
14-17: III, XI, I, II - the four I've spent little to no time with, in the order I would consider checking them out based on cultural osmosis. Do think the bits of XI's soundtrack I've heard slap.