Which is correct 'God created this world' or 'God has created this world'?

Grammatically, both are correct, but they mean slightly different things, and both may be factually incorrect.

God created this world.

: This statement is in the simple past tense and is making a more absolute statement about what God did in the past; it doesn't try to connote anything else, particularly.

God has created this world.

: This statement is in the present perfect tense; although God made the world in the past, this statement is making some kind of connection or reference to the present. The fact that God created the world has some effect still on the present.

The choice between these two tenses depends very much on your context.