Depth

The depth of your story is really the background of the story itself along with the characters. It's like hole your digging for treasure basically.

Being not so cliche also plays a role in this, because the story can go much further on its own accords. Depth is important and I consider such a requirement needed for a good and unique story as always.

Saying this simply, the depth comes from the background of your character and the involvement between other characters. Drama usually consists a lot of depth because it keeps going on and on. For it to keep going, there must be a lot connections.

When you're plotting out your characters, think about how their past led them to be like they are today. For instance, in my fanfic Exotic Nights, Kai was an angry person in the beginning, in which most readers didn't know till they found out that Kai had his eyes on Mayuko, in which she had her eyes on his bestfriend Sehun. You see what I did there?

A connection.

Another hole to dig.

More depth.