Afraid I'll have to disagree with you... I thought Diamond & Pearl was a great series (I'm actually rewatching the DVDs as I work out in the mornings), I went into Black & White with high hopes... only to have them dashed. Ash actually seems kind of dumbed down to me, as if they regressed him back into a little kid, not the trainer who had previously competed in four different leagues. Iris grated on my nerves pretty quickly, and I found the green haired kid (I don't remember his name and I don't really care to look it up) to be rather bland. And the new rival was forgettable too, nowhere near the caliber of Gary, Paul or Barry. Of course, I might be able to put up with all that if not for the absolutely dreadful way the stripped Team Rocket of their personalities, to the point where I didn't even recognize them. Even that I may have been able to overlook, except they switch over to "serious mode" for NO REASON.
And let me ask a perfectly legitimate question... if they were just going to strip the personalities away from Ash and Team Rocket, why not just have completely new characters in the first place? Seriously, if they did it right, it could have been done. Have Ash win the Sinnoh League, give Team Rocket their own moment in the sun (I dunno, they always seem to do well selling food... maybe they start their own restaurant?) and start the Black/White series fresh with new characters. Hell, you could even have an older Ash appear futher in the series as a potential mentor/rival for the new main characters.
But no. Just run the damn series into the ground instead of doing something fresh (which ironically is how I feel about the video game series lately). I gave the series a fair shot... I watched about ten episodes before giving up on it. But I can't be too upset about it I guess... I got 500+ episodes I can go back and rewatch... and half of those are actually good ones!