Justice League and Justice League Unlimited

Justice League released in 2001-2004
Justice League Unlimited 2004-2006
both ran on the Cartoon Network,  and is being shown on the CW for Kids

Justice League the series starts with a manned mission to Mars, and an unexpected incident, and the astronauts being haled as hero’s.  In time this brings together superman and batman, to come to the aid the Martian Manhunter, John Jons.  This is a 3 part story that brings the Flash, Wonder Woman, HawkGirl and the Green Lantern together and create the Justice League.  The series gives us insights to each Hero, and what makes them Heroes.
Justice League Unlimited, well continues where the Justice League ended, but for more flavor, they are adding more heroes, though there is a long story arc with an unknown government agency,  wanting to restrain the Justice League, or to bring them down.  There seems to be 2 endings to this series, one with The Flash beating Lex Luthor and Epilogue with Terry Finding out he’s Bruce Waynes Biological son.  Season 2 of Unlimited deals with Legion of Doom and the struggle of who can take over the world, or bringing back Darkseid.  Over All, this would be a great addition for any fan of cartoons, and Super Heroes.