Overall Kiseki Game Ranking

3rd > FC > Zero > CS3 > SC > Ao > CS1 > CS2 > CS4

WARNING: SPOILERS FOR ALL GAMES!

3rd: In the beginning Zero was in this spot but after more careful consideration I put 3rd first. Kevin's story is excellent, the majority of the side stories are written extremely well (carefully respecting the world Sky FC and SC have created) and have obvious literary influences which is something that most games nowadays don't have. Probably the only hangup I have is that the Doors are a bit "gamey" and the game never acknowledges if the main characters remember what they've seen in the Doors, but the content of the Doors are so good that I don't care. The soundtrack is absolutely incredible with some of the finest tracks in the Sky series and a beautiful use of the leitmotif.
https://youtu.be/BUFqkmB5SSA

FC: Hooked in the first five minutes. An extremely charming, highly focused and precise story. Forgoing grandiose setups, FC opts to keep the world and setting small, while slowly peeling back the bigger events over time while joining the plot to Estelle and Joshua's journey. A masterpiece in exercising restraint while stuffing the world full of details. A testament to Falcom's lost art of "small volume, focused quality", as players demand more and more characters, places, actions, and options. One downside is that sidequests are very straightforward and tend not to reveal too much about the world. The soundtrack is wonderfully fitting and you can tell that the composers paid serious attention to the context of every scene before writing their pieces.
https://youtu.be/s-Z65J6Se-8

Zero: This game has a bit of a slow start (what Trails game doesn't? I am totally used to it by now and use this valuable time to get scared at who will betray me) but it really pays off, with some of the best emotional scenes and dialogue in the whole series. The main story is excellently told with few flaws, such as the mystery behind Guy being delayed too much and the final boss being very lackluster. I should also mention that the side quests are tons of fun and have a much better "fun to busy" ratio than the Sky games do. The soundtrack is also incredibly top notch and is quite unique, to the point where I can identify its "sound style" almost immediately.
https://youtu.be/pmgApuXuBm8

CS3: Basically a highly refined CS1 concept. The main story and foreboding buildup is fantastic. The actors in the plot are relevant, imposing, and highly mysterious in a cool and intriguing way. Nearly all the characters are likeable for different reasons and they really stand out. Unique ending, very cool reimagining of older locations in HD. The bonding system still sucks, but the bonding events themselves are excellent. The battle system is broken to high hell, which is a bit of disappointment given how fresh the new additions are. The soundtrack is killer and exemplifies some of Sonoda and Unisuga's best talents, even if Singa had to take a dump here and there.
https://youtu.be/qmlSrtvbjtU

SC: This game oscillates back and forth in my mind as the greatest thing ever or a game with a lot of annoyances. After giving it a lot of thought and considering "what do I play Trails games for?", I have to really hand it to SC. The emotional pulls are incredible, the concept of rediscovery is really brilliant, and it does an amazing job putting the finishing touches on Liberl as a world. I also really like all the characters and their personal touches (As a bonus, this game has the most Olivier in it). This game, despite the large amount of relevant, made sure that the game didn't suffocate their development or hide away their characterization. The soundtrack is also top notch, with the best contextually written pieces in the whole series in terms of just pure volume.
https://youtu.be/KIwlj5z8gGs

Ao: While I have my reservations about the main story like the ending and post-ending sequence, but the absolute hype ramp that starts from chapter 2 onward is absolutely incredible. The side quests are some of the best in the series (along with CS3 and CS4) and elevate the shocking moments to new heights. The whole bonding system, though not as intrusive as past games, really drags things down, and this game is also where the fanservice really got out of control. Despite this, it does a great job of tying up character arcs while making sure you get surprised and enthralled with some crazy setpieces. The characters are mostly great, but Lloyd, Tio, and Elie really got downgraded into one-note characters, while Randy and Rixia managed to escape the fate of the potatoes. The soundtrack I feel is probably one of the weakest in the series, as it relies largely on Zero's soundtrack to get any hype pulls going, but hell, it's still pretty good in lots of areas.
https://youtu.be/ruEGOSQxmdI

CS1: I really enjoyed Thors campus, the student interactions, and the NPCs in general are all top notch. The worldbuilding is great, and you can really feel the buildup of the major players in the story. There is a great sense of foreboding as each chapter continues (which ends with a civil war, which I thoroughly enjoyed the reveal of the soldats), and I genuinely felt like the interpretation of Erebonia that had been shown and discussed in Sky had come to life. Despite that, the main characters were tremendously boring, and the high volume of relevant characters caused everyone to suffer from surface level depictions. Rean's character design was the "have your cake and eat it too" with the switch back and forth from self-insert psychologist to hot-blooded leader, making him the most dull potato to ever exist. Despite all the interesting story events, it was hard to get invested with the Potato Squad doing anything. The character interactions between main characters was written with such surface level writing I could never get invested (not to mention this was the first game that really pushed the full "Bonding System"), and the Crow / Rean interactions were extremely unconvincing. The soundtrack is excellent and varied, but like a lot of things in the game, the volume really worked against it.
https://youtu.be/C4JXuHiSPiU

CS2: A whole bunch of doing nothing of real interest. The plot's strokeoff on Rean is insane. I didn't find the Crow / Rean dynamic convincing in CS1, and CS2 amplifies the dynamic in a continuously unconvincing way. At least there's lots of fun things to do on a basic JRPG level, but I couldn't shake the feeling that I was completely uninvested in the Potato Squad, so it didn't change much, and the Bonding System is somehow even more intrusive than before. I was much more interested in everything outside of the main characters, and this game had very little of that. Sidequests were also not really that great either; there were lots of monster slaying sidequests which lose their luster once you begin nuking everything in sight due to the way-too-easy-to-break battle system. Divertissement was really fun and excellent, but not enough to carry the rest of the game. Also, isn't it kind of sad that the only real moment of impact in your game is when you borrow stuff from Crossbell? The soundtrack is great, a much more refined and investing soundtrack compared to CS1 with a ton of top class atmosphere pieces.
https://youtu.be/pjqhd33ZblE

CS4: CS2 Mach II. Not only does it slaughter any potential that CS3 set up plot-wise, but it seems to go out of its way to dilute any notable character drama. The potato squad reforms and gains many more members. Due to the potato effect, the main plot starts to lose any power. Like CS2 before it, the best part is the final meetup in Mishelam, where it relies on the power of past games more than its own to create something worth emotionally investing in. The sidequests in this game are really good and expansive, around the same level of CS3's excellent sidequests. The soundtrack was cheaped out to a high degree, creating contextless, heartless battle and ending themes (such as a father son relationship being represented with what sounds like a romance anime breakup song) and a lot of CS3 copycats. Still a decent chunk of great songs though.
https://youtu.be/1EZvDxkMzAg