Unlike other animes, you can just watch one piece and it won't stop!
A big pro about this anime is it's length.
As long as you have the time, you can watch a lot of it without worrying that it'll end soon.
Another great thing is the storyline. There isn't one big storyline like other animes, this comes with arcs, an island with it's History and story, with the little storyline of what happends in the world of one piece.
I've said to myself "Okay I'm gonna watch this island again for sure!" But after seeing the next one which is better "No way! This is even better!" And this is how it goes.
The soundtrack- an awesome one, many themes for many situations.
One piece started about 15 years ago, when the art was pretty "bad" but as the episodes pass the art is getting better.
For those who watched Naruto and those with fillers, One Piece doesn't have many fillers and most of it are flashbacks.
Movies! I've seen some of the sidestory movies which were good as well, like the real One Piece.
Then, "One Piece" is THE anime of all times and can be considered a masterpiece.
