Justice League Unlimited - Seasons 1 & 2 (2004-2005)
'Justice League Unlimited' is the follow up to the 'Justice League' animated series, which I saw and liked but got tired of pretty quickly. 'Unlimited' I found to be far more entertaining - it's more action packed and is much larger in scope, and incorporates a plethora of characters in the form of an expanded Justice League.
The Justice League revolves around a core team of senior superheroes - Batman, Superman, Wonder Woman, Green Lantern, Flash, Hawkgirl, and J'onn aka The Martian Manhunter - with each episode usually featuring several of them alongside several other, sometimes minor (and sometimes downright obscure) characters from the DC pantheon of heroes - like The Question, Huntress, Green Arrow, Supergirl, Aquaman, Captain Marvel, and the Atom, to name a few. It's an action adventure cartoon that naturally includes massive superhero battles, fantastical powers, and super-villains all rolled into fairly basic story structures. That doesn't mean poor stories mind you; in fact they're quite imaginative and entertaining. They are not devoid of substance either, with much of the second season story arc dealing with the power the Justice League wields and the potential that exists for them to abuse it.
'Unlimited's' character stuff is also well done, with our heroes dealing with personal demons, histories, and relationships in between bouts of smashing villains through buildings and lifting massive objects. One aspect that really makes things interesting is the tendency to incorporate more obscure characters into the stories, often making them the main characters for an episode, which nicely avoids the feeling of over-familiarity that comes from focusing on a small set of well known characters. There's good continuity between episodes and lots of references to things in DC comic lore littered throughout (of which I am only vaguely aware) that should be rewarding for fans. Although ostensibly a kids cartoon, it's perfectly enjoyable for adults as well (my kinda adults, at any rate), and there's some sharp writing and humour on offer that kids probably won't get.
The quality of animation is excellent, and the scale of events is larger than life. Way larger. The action sequences are amazing and in true comic book style feature over-the-top battles and mayhem, and I sometimes wonder how it's possible that the citizens of Earth never get pissed off at the amount of destruction these 'super battles' bring about. Last but not least, I need to mention the excellent voice work. The voice acting is absolutely perfect for the material and the sheer number of talented actors involved is mind boggling. Just take a look at the Wikipedia page for proof of the voice cast's diversity and quality.
No negatives? Not really - I can't really fault it, it's just about as good as I can imagine a 25 minute animated super-hero series being, truth be told. Sure, it's not for everyone, but for those who find this sort of thing appealing, 'Justice League Unlimited' is golden.