I, for one, only mildly enjoy Pokemon now, because the series has just been so overly rehashed too many times. But that is also why the series has survived almost ten years: it is more of the same material, although over time this material was referred to as "stuff" and eventually "crap" by some. This is partly why its rival, Digimon, is dead now: It got too complex and different. Let's take a look:
First Season: Great overall plot and interesting concept made it a smash hit with most kids.
Second Season: Similar to the first and still popular.
Third season: Began dabbling in wierd crap like kids fusing with Digimon, worlds fusing with other worlds, Digimon fusing with worlds, kids becoming Digimon, etc.
Fourth and Final Season: For all I know, there may be a hidden fifth season that nobody cares about. By then the show had become a silly Power Rangers ripoff, with the kids AS Digimon, fighting stupid villians.
However, Pokemon urged onward until now, when kids realized that the game they were playing, the cards they were trading and the show they were watching were all rehashes of rehashes of rehashy rehashes, right around the time they got Pokemon Cubic Zerconia Diamon Jade Special Limited Super Edition.
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"How are you gentlemen !! All your base are belong to us !! You are on the way to destruction. You have no chance to survive make your time. HA HA HA HA ...."
-Cats, Zero Wing (Genesis)