The Picture of Dorian Gray is a kind of morality tale, in that Basil represents God the Creator of Art. Dorian, or his portrait at least, represents Adam. Lord Henry represents Satan, he who appeals to Dorian's vanity and corrupts the lad.
It is also a re-telling of the Faust legend. In this light, Dorian sells his soul to the Devil (Lord Henry) as he falls from innocence into vanity and corruption.
Basil is the moral figure in the novel because he is the artist. He has the power to create that which is not only picturesque or beautiful, but sublime (beyond beauty). As Wilde says in the Introduction:
The artist is the creator of beautiful things. To reveal art and conceal the artist is art's aim. The critic is he who can translate into another manner or a new material his impression of beautiful things.
Basil not only creates the portrait, but he refuses to sell it. He intends to give it to Dorian. He creates art for art's sake, not more material gain. Materialism is a corruption of art.
The highest as the lowest form of criticism is a mode of autobiography. Those who find ugly meanings in beautiful things are corrupt without being charming. This is a fault.
Basil says he has too much of himself in the portrait. He realizes his folly: that he is love with his subject as much as the art. Even though he makes this mistake, he recognizes it and seeks to redeem himself by not displaying it to the public. In this, he is a true artist--a heroic protector of art.