In celebration of Netflix's live-action adaptation of the anime, I will be ranking most of the many story arcs (fillers included). These are just based on my personal opinion. So, here are arcs 10-6.
10. Sabaody Archipelago
This arc starts off with a simple story where the crew encounter Camie, a mermaid, and help her out against a gang of traffickers. This beginning dragged on for a bit which is the only reason this arc is this low on the list. Because once the crew lands on the Sabaody Archipelago, everything takes off. Here, Oda introduces so many major characters and plot points that have a huge impact on the story. The Celestial Dragons are brought in as the rulers of the world and they're instantly hated by everyone due to their treatment of literally anyone who isn't one of them. Their inclusion is a good prediction to what the final conflict of the story will be about. This arc also introduces the Worst Generation, this era's strongest pirates who have all made it to the halfway point of the Grand Line and each one will make their mark though some more than others. The scene of Luffy, Law, and Kidd facing down the Marines was an epic shot of their future team-up against the Emperors even if Oda didn't necessarily plan it when he drew it here. Rayleigh also comes in like a badass and provides more details about the mysterious One Piece which would automatically make this arc one of the best. But what really makes it the best is the theme of this arc is of slavery as the crew sees the dark underbelly of the world and the true power the Celestial Dragons wield leading to the absolute epic smackdown of Luffy v. Saint Charlos. But, of course, the crew is also quickly reminded of their place in the food chain as they go up against the full force of the Marines and Admiral Kizaru. This arc set up much of the plot for the second half of the story so while it may have had a slow start, everything after that made it gold.
9. Water 7
Some might consider combining this arc with Enies Lobby, which does make sense in a way, but seeing as the manga categorizes it into two separate arcs, the same will be applied here which is why this arc is this low. Water 7 is yet another expression of Oda's imagination as he crafts an entire city built on the water and the infrastructure built around that fact including a sea train that literally runs across the sea, something that plays an important role in this arc. It's also the arc that shows the characters' growth as a crew as their bonds are tested, mainly with Usopp and Robin, and both Luffy and Zoro prove their worth as both captain and first mate respectively. As per usual, pretty soon after they make landfall, things go south as they're soon on the run, accused and framed for crimes. The mystery just gets deeper and deeper with plenty of twists and turns. It also introduces Franky and Rob Lucci who themselves are part of the biggest twists Oda does in terms of antagonists. Franky's backstory is as heartbreaking as the others and, as always, Oda fits everything together perfectly, even the giant train-punching frog. While this arc is really just a build-up to the epic Enies Lobby arc, on its own it still has plenty of heart, humor, action, and, above all, suspense that keeps fans glued to their seats to the end.
This is one arc that many fans might deem the most 'skippable' as its impact on the rest of the story is minimal. Still, to skip it is a tragedy as this arc earns its place as one of the best. Sky Island is one of the most imaginative places Oda has come up with and considering what else he's created, that's saying something. An entire civilization living on an island hovering in the sky with a rich history of a hundreds-of-years old war between the natives and the Shandia people. Even the flashback which started out feeling like a drag turns into one of the biggest tear-jerkers of the series (Noland and Kalgara's friendship will echo for eternity). This arc also introduces the concept of haki, albeit under a different name, and the types of challenges facing the crew, especially the almighty powerful Eneru, god of the lands with the most powerful attacks seen yet. Newcomers Robin and Chopper get plenty of chances to shine in their own fights. But it's really the lore and history shown in this arc that elevates it so much to make it one of the best.
7. Impel Down
This arc is one that shows how far Luffy will go to protect the ones he cares about. Of course, at this point fans already know that but here's he is literally pushed past his limits several times. Learning of his brother's imprisonment, Luffy journeys into the infamous prison Impel Down and descends each nightmarish level, encountering old friends and enemies along the way, to save him. Bringing back fan favorite characters and introducing Fish-man Warlord Jimbei as well as the eccentric and lovable Emporio Ivankov. Buggy's a delight in every scene he's in, as usual, and Oda keeps the fans guessing with each scene over whether or not Luffy can pull it off. This whole arc is filled to the brim with non-stop action and suspense with the only real shame being that the rest of the Straw-Hats aren't here to join in on the fun. Still, the makeshift crew Luffy assembles makes up for that. Plus the Magellan and Hannyabal moments are priceless. As always, there are plenty of twists and turns that no one saw coming.
6. Arlong Park
Almost every fan will agree that it was this arc that proved how amazing One Piece truly was. At this point, it looks like Nami is a traitor to the crew and her actions from then on only seem to solidify that. But Luffy doesn't abandon his crew, going after her and learning of her tragic past and involvement with the Fish-man Pirates led by the worst of the East Arlong all to save her home. This was the arc that showed how serious it could and showed how unshakable Luffy is in his devotion to his friends. The iconic 'Help me' line is etched into fan's memories along with the following walk to Arlong Park. Luffy's fight with Arlong is nothing but epic with the final smackdown proving to be particularly cathartic. Nami's past is one of the most heartbreaking (which is again saying something) and you can feel every punch Luffy throws in her name. If you're not a fan of One Piece before this arc, you most certainly are after. This arc also introduced the Fish-men in general as well as the concept of other species and the things that await in the Grand Line. Oda just can't help with his extensive world-building. And Usopp's fight with Chew is most assuredly one of his best with his final attack being both hilarious and awesome.
And there's the next batch. Thanks for reading and check back soon for the final round 5-1.