Let me try and elaborate my feelings on this subject.
For as long as i can remember, i watched and liked the Original series. So much so that it took me a while to get used the Advanced saga and the sagas that came after it. I guess i was just so used the original group that it took me a while to get used to this whole "change in group" scenario that the series has been using for some time.
I occasionally saw Ash's adventures with May,Max and Dawn and couldn't help but think about what did happen and/or could've happened while he was travelling with Misty. For example, i couldn't help but feel that Ash's character and the general appearance of the show got a little better when Ash was travelling through Hoenn, the Battle Frontier and Sinnoh. This made me feel that the series wasn't all that good until after Misty was gone (though i tried to dismiss this thought as i actually liked the Original trio)
And then came Iris, and her "Little Kid" comments. I tried to convince myself that Misty was nicer, especially when they said that the Unova saga was a reboot of the original series. But upon rewatching some of the original episodes, i felt that Ash being mocked right and left by Misty.
Examples:
Ash Catches a Pokemon - Misty spent a large portion of that episode putting down Ash's ability to even be a trainer. Was she just ignoring the fact that Ash was a beginner, seems to me that beginners should be given a little more slack than that.
Mystery at the Lighthouse - Misty and Brock were both cutting Ash down at the beginning, not even Pikachu was supporting him
Electric Shock Showdown - Same as 1-2, no one was giving Ash any support, all he was getting was doubt and put-downs
Primeape Goes Bananas - Even Prof. Oak isn't cutting Ash any slack
March of the Exeggutor Squad - Misty made two comments that seemed a little below the belt to me; First she commented about how Melvin didn't know what he was doing and said Ash could relate to that. Then she said that Ash was bound to have at least one good idea after he made a suggestion to help Melvin. I repeat: below the belt
The Problem with Paras - Misty gave Ash a hard time regarding his Charmeleon, as did that elderly woman. And all the while, i still can't figure out why Charmeleon stopped listening to Ash, what did he do? From what i saw, Ash wasn't treating Charmeleon any differently than Charmander. Why did he stop listening to him?
Attack of the Prehistoric Pokémon - At the very end, Misty and Brock gave Ash a hard time about finding the egg. They didn't even think he could take care of an egg
The Ultimate Test - First Misty gave Ash a hard time about getting another Gym Badge, then he gets a low score on the test. Seriously, what is the point of making the main character look stupid compared to those around him?
The Battle of the Badge - Misty sure was quick to point out that Gary was ahead of Ash and seemed to care little about his initial response to it.
It's Mr. Mimie Time - Misty called Ash out on having no manners and not being helpful in comparison to Mr. Mime. That also seemed a little below the belt
Showdown at the Poke Corral - Misty sure was quick to tease Ash after he got up, and in his own home too. And his own mother just blew that off
A Friend In Deed - When Delia and Oak commended Richie's good points, Misty was quick to point out that Ash wasn't the same. That just seemed a little out of nowhere and kinda nasty too
Friend or Foe Alike - Misty wasn't even trying to make Ash feel good about the match, she was basically telling him that he didn't have a chance of winning
Navel Maneuvers - Misty gave Ash no support whatsoever in this episode. She even basically said he was stupid early on in that episode
Tracey Gets Bugged - Once again, Misty basically said that Ash's ideas are rarely ever good
Pokémon Double Trouble - Misty and Tracy basically told Ash that they knew he was going to fail. Seriously, is no one on this kid's side
I could go one to point out the ones in the Johto saga, but i think you got my point