Launching with Batman: The Animated Series, the DC Animated Universe effectively bowed out with the fantastic Justice League Unlimited, a mostly episodic series with a truly massive roster of characters. The grand finale of Justice League Unlimited somehow manages to be both a splendid send-off for the Justice League of America and the entire animated universe. With Darkseid's arrival imminent, the Justice League of America must team up with the Legion of Doom to hopefully save Earth. A confrontation that leads to one of Superman's greatest animated moments. All of Justice League Unlimited is endlessly rewatchable, but the series finale is essentially a mini movie that can stand alongside the greatest animated blockbusters on the entire DC Universe.
A major part of Superman's legacy is his allegiance with other superheroes, also known as the Justice League of America. Justice League Unlimited has a deeper roster of heroes and Superman finds himself in darker, more complex storylines. For a true distillation of what makes Superman the icon that he is, look no further than the final episodes of Justice League Unlimited.