Unlike the Nolan Batman films or even the Batman of the DC Extended Universe, the original Batman films featured one of the biggest tonal shifts from its first half to its second. While this was present in its villains and characters, it was best showcased in the presentation of Batman's hub city, Gotham. While its change from noir to neon isn't ever explained in the films, one reason for its change in style may have come from its neighbor across the harbor, Metropolis.
In Tim Burton's Batman and Batman Returns, Gotham City is showcased as a modern gothic landscape, with skyscrapers so tall they could blot out the sun. The city itself has a fair amount of hustle and bustle, but the corruption that holds the bricks of society together has put the city in a constant state of drab and noir. Batman lent himself well to this environment, as he used the shadows to fight crime. But over the two films, it was always evident that anywhere could be Crime Alley on a given day.
Joel Schumacher's Batman Forever and Batman & Robin took a new turn for the city, and rather than showcase its darkest corners, a more vibrant tone was introduced. Now, neon had become the backdrop for evil in the city. Everything about it had taken to the skies, with buildings like the Gotham Observatory being held up by a massive statue reminiscent of Greek Gods. It became evident that this Gotham was trying its best to rise above the corruption it started as, and the presence of Batman and Robin helped with this considerably. But how did Metropolis play a role in the city's transformation?
In Batman Forever, Bruce name-dropped the city to Dick Grayson as he was about to leave. In that instance, it was clear that the technologically advanced city was an entity in this world and was enough to get fans asking questions. Superman was then name-dropped in Batman & Robin, further showing that Metropolis was more than a random city. It's likely that as STAR Labs and Superman made their mark on the city, these advancements turned it into a futuristic art deco style similar to Superman: The Animated Series. Since its crime and corruption never held the city down, Metropolis advanced much faster.
As Batman made more of a difference, Batman Forever represented Gotham's attempt to advance as well, with statues lifting its city to the clouds, rising above the crime below. But in reality, it created a society where people tried to avoid the lower levels, as that was where crime was rampant, and the villains took control. As a result, rather than advance like Metropolis, Gotham just added another level for colorful gangs and villains to try and control. The only real silver lining is that Batman had seemingly freed the city from its mob connections, allowing it to evolve.
Although he never physically appeared in the films, Superman's influence and his promise of a brighter tomorrow likely impacted Gotham City on a massive scale. The city literally rose above it rather than clean up the crime, changing itself forever. That said, its crime evolved as well, with new enemies and bigger stakes. Nevertheless, if true, Metropolis' influence on Gotham City further shows just how important the city is in any universe.