The early seasons certaingly did have an arc, for one thing, one whole episode was a midquel to "Metwo Strikes Back", before midquels were ever a popular idea in the medium and applied to things like "The Lion King 3/12", you could sense the writers at least wanted to try something with the show. Advanced likewise had a good arc when it began (Team Aqua and Team Magma), but threw it out once they developed it.
I agree, The Orange Islands explored the Pokemon mythology of the existing Kanto Region information, coupled with small things about the rest. Whilst they arguably make it up as they go along, the early storylines stuck the closest not just to the games, but to less restraint on censorship. Not even Japan does the much riskier stuff like James man-boobs or Poregon anymore.
"Battle Frontier" ought to have been Ash's final season, he tied with May in the finals of a tournament in his home town, Misty was seen to be waiting for him at the beggining of that season when he came home, it made more sense to pass the torch to May and settle down, maybe even give her Pikachu and Brock to tag along so there was something of the old mixed in with the new, but no, instead, May (whose character gained the respect of the fans for replacing Misty), is kicked to the curb and the same will happen to Dawn once her three years are done with around the release of the next game.
It's the repetition that definatly kills it, but that can be remedied with a new way of interpreting the episodes with fresh characterisations, that obviously isnt going to happen
