It quite different to Naruto and Bleach, which are more action-centric and well, fan pandering. The thing about One Piece is that it's just fun; there are more jokes, while the visuals and character designs are eccentric in comparison. It has some incredibly heart breaking drama and tragedy, and resonates more with the viewer because of the relationships shared by the characters.
It's essentially about a group of friends looking to embark on a great adventure; each have their own ambitions and dreams, and by moving forward with Luffy, they ultimately step closer to touching those dreams. It is often epic in scale, the Straw Hat's adventures take in entire countries, new races of people and even a floating land in the sky.
I really love One Piece. Whether or not you like it will depend on if you can take the very loose artistic style of art work (no hint of realism, it is a full-on cartoon) and the fact that Luffy is just so positive and happy. He is by far and away my favourite SJ lead character simply because he never stops smiling.
I pretty much knew I'd love One Piece based on the following image.