The main human characters of the MonsterVerse movies tend to be involved in some way with Monarch, an organization that tracks and studies the gargantuan monsters of the stories, known as Titans. So the average IQ of the characters is often competing with some of the super-geniuses of the MCU.
Some of the main characters from the movies, however, are smarter than others and this ranking reflects their overall intelligence, whether it ultimately be used for good or for bad.
Ford Brody
Ford Brody is an Explosive Ordnance Disposal Technician in the US Army and is thus well-positioned to be close to the action in the first Godzilla movie, which is great for the audience and a little less great for him. Nevertheless, Brody's wits and bravery get him out of many tough situations.
Unlike most of the main characters in MonsterVerse, he has absolutely no interest in the Titans themselves and really just sees them as obstacles. He's clearly resourceful and intelligent but Brody's mission is never to really understand more about the world around him but rather to just react to it so he can get back to his family.
Mason Weaver
Mason Weaver is a self-described anti-war photographer and one of the few members of the expedition team in Kong: Skull Island to make it through the ordeal. She's also one of the few characters shown to have an observable bond with Kong, even if it is relatively slight.
Most of Weaver's power in the story comes from observation, and she does end up putting herself in harm's way more than is necessary, but the clear emotional intelligence that she exhibits shouldn't be discounted.
James Conrad
James Conrad is very similar to Weaver in terms of overall intelligence and temperament, quickly striking up somewhat of a rapport with her, but trumps her in terms of situational experience relevant to their predicament on Skull Island.
As a seasoned former military turned-mercenary type, Conrad clearly has excellent survival skills and a clear and pragmatic way of thinking, even in the most distressing situations. He also demonstrates on several occasions that he appreciates the movie's core concept of violence not being a useful solution in every situation. However, like Weaver and unlike most of the soldiers, he has no actual reason for placing himself in danger by going to Skull Island. In fact, he's one of the few people who seems to understand how dangerous the mission really is, yet goes anyway. Hopefully, Conrad's experiences on the island in some way free him from his quasi-death-wish, but there's no guarantee of this.
Jia
Jia is a young Iwi girl who is orphaned by the severe storms that surround Skull Island and develops an attachment to Kong, appearing to be the person that the Titan trusts most.
More than this, Jia is the only person able to fully communicate with Kong, using a combination of sign language and a clear emotional intuitiveness to have conversations with him and even influence some of his biggest decisions. Jia's intelligence is, therefore, an unspoken one that is more felt by the audience through her actions.
Madison Russell
The daughter of Dr. Mark Russell and Dr. Emma Russell, Madison is too young to really be counted among the academics who make up the smartest human characters of the MonsterVerse. However, they more than hold their own in extraordinary circumstances and show a deep knowledge of not only the Titans but of advanced technology used to locate communicate with them.
Madison is involved with the antagonists of Godzilla: King of the Monsters but only through her mother as she's still too young at that point to be much more than a passenger in the course of events, prompting her to grow up quickly and take matters into her own hands several times in order to try and save lives. In Godzilla Vs. Kong, they're more of an outsider to larger events, but that doesn't stop them from uncovering the villain's plans.
Dr. Nathan Lind
The leading authority on the Hollow Earth that's mentioned throughout the MonsterVerse movies, Dr. Lind is largely discredited when he's first introduced at the beginning of Godzilla Vs. Kong but he's ultimately shown to be correct in all of his theories, even with his more spur-of-the-moment and on-his-feet ideas.
Dr. Lind leads the movie's expedition into the Hollow Earth and proves both a competent leader and pilot, despite his fish-out-of-water vibe whilst assuming the role of a hero and an endearing degree of awkwardness.
Dr. Mark Russell
Dr. Mark Russell is introduced into the MonsterVerse at the beginning of Godzilla: King of the Monsters and is initially an animal researcher clearly searching for some stability in his life after the tragic death of his son. He also helped to build the prototype of the Orca device that can communicate with the Titans.
After discovering the secret of a bioacoustic alpha signal developed by his ex-wife, Dr. Emma Russell, and discovering a new understanding of Godzilla, he helps to defeat King Ghidorah and rejoins Monarch in a more senior position, leading the organization's responses in Godzilla Vs. Kong.
Dr. Ilene Andrews
Dr. Andrews is the chief Monarch scientist studying Kong on Skull Island at the beginning of Godzilla Vs. Kong and became the guardian of Jia following the death of her parents.
While Jia is one that communicates with Kong, it should be noted that Dr. Andrews is the one that actually teaches Kong sign language and her understanding of the Titan in an overall sense is second to none. She's very much the Kong-related equivalent of one of the MonsterVerse's most revered figures and the next entry on our list.
Dr. Ishiro Serizawa
Dr. Serizawa, along with his protege Dr. Vivienne Graham, is the audience's introduction to Monarch and the general lore of Titans in the MonsterVerse. He's a fittingly learned and wise figure.
The character is an interesting spin on the Dr. Serizawa from director Ishirō Honda's original 1954 Godzilla movie and makes frequent pleas for humanity to consider naturalism as an option, seeing the Titans as a manifestation of the ecosystem balancing itself. It's an interesting position that's echoed frequently throughout all of the MonsterVerse movies and taken to its absolute extreme by our next entry.
Dr. Emma Russell
A brilliant paleobiologist who takes a rash course of action, Dr. Emma Russell enhances a project she began with her ex-husband, Dr. Mark Russell, into a communication device that can, to an extent, control, or influence, the Titans by using bioacoustic signals.
Though she uses methods that ultimately make her a villain, and she makes a grave error of judgment in releasing King Ghidorah, her understanding of the Titans, in general, is rivaled only by Dr. Serizawa. She's recognized as one of the greatest minds of the MonsterVerse while she's alive and remembered as one of the most pivotal figures in its development after she dies.