For most manga readers, One Piece needs no introduction. The story that Akira Toriyama wishes he wrote, One Piece is basically about a bunch of silly pirates who call themselves The Straw Hats and the adventures they have. The Straw Hats are Monkey D. Luffy, who is even sillier than his name, Roronoa Zoro (or Zolo, in the english version), an I-don't really-care type master swordsman, Nami, a thieving navigator, Usopp, a tall-tale spinner, Sanji, a badass cook who is awkward around girls, and Tony Tony Chopper, who is sooooo cuuuuute! The story centers on the core Shonen Jump principles of yujo, doryoku, shori (friendship, perseverance, victory), as well as unique themes of dreams and high adventure. Oda's unique storytelling method sets One Piece apart from the rest of the pack, cramming every other panel with enough information to fill several hundred volumes of Naruto, in a style a style similar to saturday morning cartoons such as Looney Tunes (there's even ultra-violence that somehow leaves no-one affected!). Needless to say, One Piece has been made into a saturday morning cartoon. But with all that unfiltered silly, is it possible that One Piece is a genuine drama, with authentic characters and powerful, maybe even deep, metaphors? Strangely enough, the answer is yes.
Take, for example, this scene in volume 24 (part one of Skypiea). The crew is having basically a little down time, when suddenly... A SHIP FALLS OUT OF THE SKY!!! That is, of course, very silly, but it is not a joke. This moment is surprisingly tense, as the Straw Hats run to save themselves from a threat they can neither avoid nor comprehend. But a tense moment does not get a series taken seriously (is Bleach serious? InuYasha? DBZ?), and really this moment WAS kinda silly. In my books, a series should not be taken seriously (serious fun being beside the point) unless I can take the characters seriously. Fortunately, I can.
Looking at another scene in volume 24 (which I happen to have right in front of me), Luffy and crew make a stop at the pirate village "Mock Town" and encounter the evil pirate Bellamy the Hyena and his crew of mean jerks at a bar. On a whim, Bellamy beats Luffy within what at least looks like an inch of his life, renouncing the principles of dreams and adventure that The Straw Hats hold so dear as rubbish ("'They were lucky to die chasing their dream!' Ha ha ha!! I SAY THEY'RE LOSERS!"). The Straw Hats walk out of the bar, devastated. However, as they are about to leave, a big guy sitting in the middle of the road who Luffy encountered earlier (later revealed to be Blackbeard himself) looks at them with a big toothy grin an proclaims "PEOPLE'S DREAMS TO NOT DIE!" This
You see, Oda has figured out something very smart that even the most gifted of the current SJ writers (Kubo, Ohba/Obata, I'm looking right at you guys) fail to grasp. Fighting does not make a story automatically gripping, nor does a reality based scenario. What does is a believable, emotional, and relatable set of characters, and this Oda excels at. Every character is a living, breathing person, and because of this I take One Piece seriously.