I'll give you Dawn and your implication that May was the worst girl before her, but other than that, I'm not so sure.
I don't like AG's turn-out (heck, before BW, I considered THAT the worst series ever for a variety of reasons, including Misty's departure, the butchering of May's character, basically depicting the Hoenn Gym Leaders as total pansies comparable to Team Rocket in Ash Catches a Pokémon [which is made even worse in light of the poorly written reason behind Misty's departure], basically Team Rocket not actually being depicted as actual credible threats and if anything Team Magma made their presence completely unnecessary, Brock having even less use than in Johto [and considering he had little use in that region despite the games Johto debuted in basically introducing the breeding mechanic, that's saying a lot], and, of course, Ash basically not increasing in rank, especially worse when Johto basically HAD Ash increasing in rank.), but at least Ash didn't decrease in rank at all in that league (not that it makes things any better, since it also means AG was effectively skippable as a result), while in BW, Ash did decrease in rank, and worse, he lost to someone who was a total idiot, making even BW Ash seem smart (and keep in mind that series basically seemed to give him brain damage, making even Indigo League Ash seem like a genius.). Say what you will about Tobias, as I'm ticked off at Ash losing to Tobias and his legendaries (especially Pikachu losing in light of the Regice battle where he effectively defeated it with little effort), but at least he actually knew what he was doing and more importantly was not a complete idiot. You don't like DP? Fine, but at least acknowledge that Ash at least improved in DP, especially when in the league before that, he didn't improve at all.
Besides, even Original Series Ash didn't mistake a human being like Iris for a Pokémon like Axew. And honestly, having Ash lose to Trip, twice, despite his actually being much more experienced than the latter who was LITERALLY just starting out (and the second time didn't even have Zekrom as an excuse, not that Ash not knowing about Pikachu's disability should even be used as a reason for the first loss since it came right after he had his butt handed to him by Team Rocket.), was just the worst turnout.