I don't know where to read, but it seems to me that end of the 90s, TV shows (real and anime) became less episode based but got a whole story arc, like we know from current TV shows like "Game of Thrones", "Breaking Bad" or "The Wire".
I always hear people talking about how "The Sopranos" was the first TV show that did this, but anime like "Neon Genesis Evangelion" and "Cowboy Bebop" came out years before it.