In during Naruto. Obvious answer, but it's not like anyone else who's first experience with anime belonged to Toonami will stop watching.
The Froad said:
I'd say Pokemon. Say what you want, but it is crap. It's been crap for the ten years I've seen it. I collected the cards for a couple months, but that's it.
Pokemon isn't overhyped as an anime, but it is amongst the scene communities by the usual means of "remembering the childhood you never had." Also, why you would even bother analyzing Pokemon as means of a "serious anime" is beyond me.
Death Note has been seeing an increase. I personally liked Death Note, it's a shame the fanbase overlooks the excellent mind-****ery the character engage in in favor of how "kawaii" L happened to be looking at the time.
If the average "anime enthusiast" demographic in your area happens to be pre-teen Mexican children, then oh yes, Yu-Gi-Oh is certainly overhyped.
Lucky Star is just stupid, the opening was the only thing liked and that wasn't even that good.
I enjoyed Lucky Star for it's simple yet witty humour piquing at the lifestyles of "otaku." The series also really grows if you're the type who understood the truckloads of anime references within the series such as the inclusion of Meito Anisawa and Shirashi Minoru's "Wasuremono" song.
Animes like Cowboy Bebop have a huge fanbase but since it is a great anime and does not last 168 episodes it's not (or was not) considered over hyped.
You seem to argue that an anime's greatness derives from how long the series runs. Hokuto no Ken drew on for 158 episodes, and by far I would describe the plot and characters to be deeper than anything I've seen in Naruto. "Emo Ninja Who Wants to Govern His Village" has nothing against "Hot-Blooded Man Who Seeks Peace in an Post-Apocalyptic World, and Seeks to Change it With His Fists."
tl;dr, Anime becomes overhyped because the fanbase has nothing else. Of course if someone happened to watch Adult Swim's newest anime, they would automatically perceive it as "good," assuming this person has little or no experience to other anime. Sometimes they do, but most of the time, they also automatically perceive it as good, because apparently, watching more anime makes you a better otaku, which wins cool points on the internet.