First of all, because he became this big and famous from nothing. He started on his own. No professionals or musicians to help him through. He rised alone at 16 years old.

Second of all, because he got trough all the hate, he didn't care, he made good to humanity and didn't ask for anything in return. 

 Because he loves his fans, because he takes care of them, because he treats them like family, because they're his everything, because he's grateful to them.

Not trying to be mean, I adore 1D, but they will never be as good as him, no matter how famous they get. 

Why not? Well, because this:

Or because:

"Recently pop Justin Bieber has been awarded for his help in reducing American teen suicide; the 19 year old singer’s song off his most recent album BELIEVE reduced American suicide over 17% percent ! On not only one, but two of his songs, he decreased American teen boys & girls suicides together on both songs, Be Alright and Believe. A study was taken showing that both helped save the life of 17% suicidal teens PER SONG ! That’s over 34% of teens saved thanks to Bieber!"

In 1994 Michael Jackson said that in that very year the only person who will be able to take his place is gonna be born. What a coincidence that Justin was born in 1994.

Not just because of this, or because of how many awards he's got, or because he's the most followed person on twitter in twitter's history, but because he's a good person. Because he goes to hospitals, makes charity, helps unfortunate kids and takes care of his beliebers. Because we got to the point where we make fun of Justin and he makes fun back. Because he's the only person that can make twitter go nuts without even being online (prooved fact ) Because he follows us, because he sneaks us in into meet&greets and concerts, because he adores us, because we adore him.