Ash and Misty's compelling relationship as trainer and gym leader was actually improved upon later on in Pokémon XY. This comes despite the fact that most fans who grew up watching the original anime series back in the day understandably believe that everything after the Kanto region doesn't count or is nowhere near as good.
Although the original series' Brock also led his own gym, Misty's relationship with Ash in Pokémon was so unique because she ed Ash's quest before they battled over the right to her gym's Cascade Badge - and Ash wasn't aware even aware she was a gym leader. It isn't until the episode "The Water Flowers of Cerulean City" that Ash learns the truth about her credentials and battles Misty in her own gym.
In Pokémon XY, Ash undergoes the same type of match against his traveling companion Clemont in the episode "The Moment of Lumiose Truth!" But unlike his battle with Misty during the original Pokémon series, Pokémon XY built up to Ash and Clemont's official duel over the Voltage Badge for much longer and far more effectively than the first season did with Misty.
Clemont is More Mysterious Than Misty
Undoubtedly the original series' main failing lies in how the entirety of Ash and Misty's unique relationship as trainer and gym leader lasted over the course of just one episode - only after having just met six installments earlier. It wasn't until the iconic "Water Flowers of Cerulean City" episode that Pokémon really hinted that Misty was more than just another trainer when she begins acting strangely upon learning that Ash is headed for Cerulean City. And although she mysteriously disappears for a short while when Ash and Brock first arrive in the city, she quickly reappears in the same episode after her sisters are about to just give Ash the Cascade Badge without a fight.
In contrast to Misty's storyline, Pokémon XY built things up over a much longer period of time. After Ash and Clemont meet in episode one of season 17, it isn't until halfway through Pokémon season 18 that Ash and his friend Clemont finally battle in the Lumiose city gym, and Ash knows that Clemont is a gym leader this entire time. Moreover, Clemont ends up leaving Ash for much longer than Misty does before their long-awaited battle (Clemont is gone for five episodes to prepare as opposed to a few minutes like Misty), enhancing viewer suspense even more.
In fact, a "side story" in XY that postpones Ash and Clemont's battle even longer lasts for an entire episode when the original series followed its usual formula by having Team Rocket interrupt Ash and Misty's match for a few minutes. This unique approach on Pokémon XY's part not only extended viewer suspense for even longer, but allowed Ash and Clemont's match to go uninterrupted in "The Moment of Lumiose Truth!" with Team Rocket not showing up. Of course, Team Rocket's involvement in Ash and Misty's battle did serve a very important purpose in that they make it believable how a trainer with such little experience could beat seasoned veterans. Partially what made Pokémon's early episodes so effective was that Ash sometimes won badges due to some technicality that was often because of Team Rocket. This not only justified the annoying trope in most anime where the hero always wins and also allowed for Ash's later victories to be more impactful when they happened for real. So even though Pokémon XY can't beat that aspect of the original series, it has successfully improved upon many other aspects, including the relationship between Ash and Misty.
