‘Superman’ Review: James Gunn Gives DC Studios’ Crown Jewel a Gleaming Polish With Help From David Corenswet and Rachel Brosnahan

From his breakout as writer-director, Slither, to Guardians of the Galaxy, James Gunn has made it his mission to lighten the oppressive darkness of so much contemporary sci-fi with irreverent humor and the exhilaration of an unabashed genre geek. For his first entry as new co-chair — alongside producer Peter…