I've been thinking and actually is kind of really hard to think of an specific TV show that i can call my favorite, but if i must choose one i think it might be neon genesis evangelion.
it may be not be considered a TV series in the traditional sense, because its only twenty chapters, and is an anime, but it just has this special vibe through the whole thing.
i believe that it's special, because it starts as a normal mech anime, with gigant fighting robots, and very stereotipical characters, however as the story advances we discover that there's much more to it, with dense and intense topics such as the relation of the human race with god, the origin of the human race, and the achivement of a superior fase of evolution that takes away the limits of existence itself.
Amazingly many people didn't like the ending, and while it's true that this is very open to interpretation, it didn't deserve to be bashed so badly, because of this ending there was a movie released called "The End of Evangelion", which gave a more traditional ending to the dissapointed fans. a whole lot of time after that, they released more movies, which were suposed to be the original story with new drawing techniques, however after the second of this movies (there are four movies scheduled in total) the story changes, and in my opinion this change isn't positive at all, as it ads just fan service and useless stuff like time travel.
So in general i believe that evangelion marked a path towards more serious anime, and confirmed this medium as a valid source of serious and adult material.
