1. Team Rocket should have been more serious from the start. I found it annoying about how easy it was to predict half the episode before it started.
2. Wish the Kanto/Johto Leagues were given better results than T16.
3. I would have liked to have seen Barry and Paul continue into Unova. I liked how Ash had a rival that was his counterpart and then also someone who resembled him too.
4. Misty should have continued at least into Hoenn. She is obviously the most liked out of the four female main characters.
5. I personally didn't like Hoenn that much. It's my least favorite region so I would have to say that besides most of Ash's pokemon evolving (or all can't really remember) I would have liked to see a lot of things change. I noticed this was the region where Ash started to learn lessons he already dealt with in Kanto.
6. Ash's appearance in Unova makes it look like he got younger. At the end of DP you could make him out up to a 15 year old possibly. In Unova I look at him as a 10 year old for sure. Sooo basically the age thing everyone talks about for this point.
7. Brock's departure from the show could have been handled better.
8. Dawn (along with Misty) should have gotten another region to travel in. Not sure if the Contests battles were really unpopular or something but Dawn still was a good part of the group.
*9* MY BIGGEST CHANGE! I would like to see Ash go into a battle with a strategy from the start. It seems like every battle he starts off with a regular attack, then has to try and stop his opposition's strategy and then he figures something out. I've always felt like his rival in his respected region always outsmarts him for 90% of the match, but that 10% Ash outsmarts his rival, Ash somewho will get the win half those matches.