Wired has a list of things to consume “Instead of Man of Steel”. I still plan to go see Man of Steel tonight, so I can’t speak to whether their suggestion that the omission of that movie is sound, but I think the advice is otherwise good.
Just last night, I completed watching all of Justice League and Justice League Unlimited with my daughter, and am impressed at how well this series holds up. It manages to take even B-list characters and tell great stories around them.
While you’re at it, watch all of the DC Universe animated movies; they’re almost universally excellent, and better than most “real” superhero movies.