First of all, no good versus evil. I love moral depth, like Death Note.
Second of all, a Drama that's strong enough to bring or kick the tears out of you, like One Piece.
Next, comedy. And lots of it. Comedy that's strong and present enough without harming the main plot development, like One Piece.
Next, mysteries. Lots of them. Especially those which need like a hundred chapters to get even a slight hint. Like One Piece... Again.
Next, friendship encouragement. Something that proves that a man can love another man as his friend and brother without it necessarily being gay or girly. Like what Naruto does for Sasuke.
Next, that same friendship being torn between principles. Like in Naruto.
Next, Love. Lots of love. Strong enough to be there without harming or slowing the plot development down. Like Full Metal Alchemist Brotherhood, like Sword Art Online and like Bakuman.
Next, battles. Action is very important. The more emotional, epic and exciting the battles are, the better. All emotional aspects of the series should be included in the fight, like The Straw Hats vs CP9, or Naruto vs Sasuke in the Valley of The End. That makes the battle something worth watching, and something people will keep doing Youtube Videos from. Over and over again.
Next, a great animation with even greater music. Nothing like the shitty work Pierrot has done with Naruto. Something like Full Metal Alchemist Brotherhood, where not even a single battle in the whole 64 episodes was badly animated. One Piece is a good choice, kind of.
Next, all characters important to the plot should have a full character development, since the moment they were kids, to the moment they are now. Something like One Piece, where all the Straw Hats' history is known and helps us love each character.
Lastly, what a great story really needs, most importantly, is being able to have a fulfilling ending. Harry Potter was something that ended an era, a whole phenomenom. And yet people still cling to it. Same with Dragon Ball. Full Metal Alchemist. Death Note, to some extent. A great story has to have a great ending. Usually, an ending that makes you A) Feel unusually happy about life, and B) Want to see the whole series again, or read the story from the beginning.
