20. Justice League Unlimited

After years of jokes about the old Super Friends cartoon, and more than one aborted attempt at filming a live-action version of DC Comics' famed Justice League, the greatest heroes of that universe were finally banded together by the mighty power of animation guru Bruce Timm (Batman: The Animated Series, et al). It was almost too much for a fanboy to hope for, not just incorporating the Bats and Superman seen in their previous Timm-produced series, but also bringing in the core group of Martian Manhunter, Wonder Woman, the Flash, Green Lantern, and Hawkgirl -- several of whom were new to the modern world of animation.

The show, basically, rocked, and for its first two years it was known simply as Justice League. But for its final three seasons it morphed into Justice League Unlimited and expanded its basic roster of seven to cycle in a multitude of DC heroes, with the main players still getting their fair share of screen time too. (Fifty characters appear in the first episode alone, setting the tone of the revamped series.) Standalone episodes and arc storylines were mixed together, including epic battles against a government organization called Project Cadmus and, in the final season, against the Secret Society (a.k.a. the Legion of Doom). Great, great stuff for even non-comic book fans.