Favourite arcs:
1/2. Tenrou arc: culmination of a lot of plot points that happened until that arc, like TOH/Jellal, Ultear, cults of Zeref etc . Hades is the 2nd best villain of the series IMO, and the fight of Hades vs everyone was amazing. First time Gildarts engaged in an actual fight. First time Zeref and Acnologia made appearances. Set the groundwork for the next. Lore wise, the arc which had the most info bombs, executed well too. Many other iconic moments like Gildarts flexing his MP, Laxus' amazing comeback etc
Could've been the undisputed number 1 arc, if not for Natsu vs Zancrow and Erza vs Azuma, those two were BS
2/1. Tower of Heaven arc: culmination of many plot points until then, like Seigrain, Ultear, Galuna/Deliora etc. The plot was great. Jellal was an amazing villain, both manipulative and powerful. First time we got to see a Wizard Saint facing the MCs. Erza's backstory was good. DF was introduced. We got to see why the magic council stood above all, with a country buster weapon at their disposal. Also, main villain actually off'd someone on screen for a chance.
3. Dragon Festival arc: Officially included within GMG arc, separating it from GMG since it doesn't have much relations to the GMG itself, except that the planning/execution was happening within the events of GMG. Also because GMG was a disgrace.
Future Rouge is one of the best villains of the series, extremely powerful, intelligent and manipulative. He subverted the royal family into opening the floodgates for the dragons to swarm. His plan would've been successful if not for future Lucy, whose timeline he ruled, commanding 10,000+ dragons to destroy everything in his path
Future Rouge one shotting LFD Natsu amp'd on POF was a treat to watch as well. Also a main villain who actually killed - most of the main cast in Future Lucy's timeline, Future Lucy in current timeline.
GMG dragons were freaking amazing. This was the first time we got a glimpse of the unbeatable, overwhelming power of the dragons; a glimpse of the punishing and hard times of human society many hundred of years ago. They were so powerful that even DS of Laxus' caliber were utter fodder to them. We could feel the utter helplessness of the situation, when we saw the humans and DS alike losing ground to dragons who were playing around, eventually leading to their deaths (all of which got reversed by Ultear's sacrifice)
This arc also foreshadowed a grim future, where Acnologia returns to be the sole ruler of the planet, annihilating everyone in his path
Cons: time travel logic made no sense. Future Rogue's reason for getting possessed by his shade
4. Phantom Lord arc: guild wars, Jose and Gajeel were amazing, with how villainous they were. Gajeel's crucifixion scene was especially impactful. Gajeel vs Natsu is a contender for best fight of the series IMO. Jose vs Makarov, clash of the Wizard Saints, ending with Fairy Law, was another iconic moment of FT
5. Battle of FT: guild civil war. Laxus was absolute greatness, the overwhelming dominance, chad persona, the planning etc. The arc where villains planned and executed the best, only next to Mard, Future Rouge and Jellal in this regard. Freed was great, his magic and powers were unique, and laid the foundation of the entire arc. Also gave us one of the iconic moments of the series with his fight vs awakened Mirajane. Loke/Lucy had a good fight as well ahh, back when Lucy wasn't fodder, ironic that it was also the time Lucy was a newbie
Cons: Bixlow and Evergreen didn't live upto hype. Mystogan vs Laxus was hype AF, but got interrupted.
6. Oracion Seis arc: introduction of the first major dark guild of the series. A group of villains where all of them lived upto their hype, and needed teamwork/strategy to be beaten. Gave us some of the best fights of the series in terms of execution. For eg: Erza vs Midnight (her best fight of the series IMO), Gray/Lyon vs Racer. Zero was a decent final boss, had a great battle vs DF Natsu. The concept of seals around Brain/Zero, and OS members' connection to TOH were nice touches.
Con: Jellal. His intro was hype, with his swiftly dispatching Natsu and self destruction circle about to one shot the entire Nirvana. Then he turned into a pathetic cry baby, had amnesia plot device. This arc set in motion Jellal's transformation from greatness to JelLOL.
Neutral/All right arcs:
1. Galuna arc:
Gray's backstory with Ul/Lyon/Deliora was nice. Lyon was decent, but didn't live upto the hype. Deliora was AMAZING even though he didn't do anything, he set the standard and hype for the demons of book of Zeref with his overwhelming presence
Lyon's three underlings were a disappointment.
2. Tartarus arc:
The plot was great, the guild initially did a good job setting the tone of the arc, by destroying the council and subverting it's top official.
Mard is THE best villain of the series (IMO), he has got everything - great powers, persona, intellect, looks. Overall, just the GOAT. The plan for taking out the council and reviving END was one of the best executed plans in the series, and would've been successful had it not been for extreme wild card he could've never foreseen - dragons coming out of DS to destroy face.
He also had some iconic moments with his fight against CSK and the hundreds of years long rivalry between them, as well as him stomping LFD Natsu + twin dragons by sitting on his chair in his base.
Acnologia and Zeref both making their appearance, first time since Tenrou, was also extreme hype. This could've easily been the last arc of the series, if Mashima planned well and executed, demons from the book of Zeref being Zeref's lackeys for the final arc would've been so fitting.
Tartarus arc's impact on protagonists was so big that it gave PTSD for the members to train like they never did in their life, and prompted Makarov to disband the guild all together
So, why neutral/all right? Lets me get into the cons.
Cons: the demon gates were TRASH. ALL of them. Tartarus were the strongest demons from the book of Zeref. Deliora had set an amazing standard for the overwhelming power of the demons from the book of Zeref, he was an unstoppable natural calamity! The legends surrounding them were such that cults formed around them, trying to get hold of the books of Zeref. And what did we get? Puny humanoids, who were all <= the main cast of FT. WHY? Such a massive disappointment.
Gray getting DeS magic from Silver was an asspull, made no sense. But at least it gave Gray some relevancy, so whatever.
3. Zentopia arc:
The plot was decent, tied nicely into why Lucy/Yukino were important to the crown in GMG (since all other celestial spirits got off'd by OS). Oracion Seis were decent villains. Enjoyed Erza vs Cobra, Mira (Sitri) vs Racer & Mary, Gray vs Angel. The OS members making personal sacrifice in exchange for power was a nice touch as well
Gildarts vs Byro was also good, showed Gildarts as a physical beast for defeating someone who basically trained all his life purely on physical combat.
Trash arcs:
1. Averez arc:
Had potential to be the best, Became the undisputed worst arc of the series. Not going to do in detail, since the list is endless. Zeref, Acno and Spriggan 12 were all trash.
2. GMG arc:
Amazing setting and buildup, poor execution. A tournament with all guilds in the country could've been amazing if executed. There were still hype moments in the arc, like Bacchus, Kagura, everything surrounding Sabertooth; but all butchered.
Twin dragon vs Natsu/Gajeel destroyed all hype of Sabertooth by having base Natsu solo their DF, it didn't matter if Mashima tried to save their reputation by giving them massive powerups later on, the damage had already been done, irreversibly. They would never recover from that humiliation.
Jellal vs Jura, a WS showdown, got interrupted for BS reason. If anyone would've recognized Jellal, they already would've because of HBM, like Jura did. No reason to stop it anymore.
Raven Tail was a massive disappointment.
Laxus vs Jura, another extremely hyped match, was off screened. WHY? Laxus copying Natsu's catchphrase. WHY?
Sting giving up in the end - icing on the cake.
2nd worst arc of the series. This was the arc that saw the highest rate of people dropping the series. The only saving grace, by the end, was the entire plot being setup around Future Rouge, dragons and the royal family
3. Avatar arc
Waste of time dealing with a bunch of fodder. The avatar of the war god was hype and had amazing design, only to be one shotted. ATLA face junior.
4. Celestial Spirit corruption arc: (?)
Don't remember the name. The arc where celestial spirits go bad. Like the premise, that there were consequences to celestial spirits getting involved in Eclipse Gate, didn't make much sense. And the fights were boring for the most part, evil Loke with black light was somewhat interesting tho