"God saw that the light was good..." Gen 1:4a "And God saw that it was good..."Gen 1: 19, 21, 25.
Which begs the question: Good for what?
I suggest three things: 1) Good for man to live in 2) Good in and of itself as it expresses something of who God is. 3) As Robert Jenson (see above link) suggest: A good stage for the drama of Jesus Christ. Which in a sense links again into No. 2.