Given the sprawling nature of both the Marvel Needs To Wait Until Phase 5 Before X-Men CrossoverThe X-Men have naturally been making most of the headlines, given the long-standing success of the X-Men movie franchise and the popularity of its characters. Meanwhile, the Fantastic Four have been somewhat overlooked, given that there have already been three Fantastic Four movies in the past couple of decades, and they've from bad to outstandingly terrible. However, the Fantastic Four would arguably be an even more valuable addition to the MCU than the X-Men - not to mention a considerably less messy one.This Page: What the Fantastic Four Offer To The MCU
What the Fantastic Four Offer To The MCU
In a way, the fact that the Fantastic Four haven't had a really great movie adaptation yet is one of the biggest points in their favor. It would be very difficult for Marvel to find a new Professor Xavier after Patrick Stewart spent seventeen years making the role his own, but few people are particularly attached to Jessica Alba's Sue Storm or Miles Teller's Reed Richards. Needless to say, 2015's Fantastic Four cast can't be integrated into the MCU even if Marvel was eccentric enough to try it, since Johnny Storm actor Michael B. Jordan became Black Panther.
Logistically, adding the Fantastic Four to the MCU would be quite straightforward. Unlike the mutants, these characters don't have a long history of gradual emergence into the public eye. They're simply the result of a science experiment gone wrong, and those sorts of things happen all the time in the MCU. An MCU Fantastic Four movie could even incorporate existing elements from the mega-franchise's history - for example, by having the team use discarded Chitauri technology or Stark Industries advancements in their ill-fated space mission.
Crucially, adding Reed Richards to the MCU would also open up the franchise to Thanos and the Infinity Stones - they're just not talking to each other.
What X-Men Offer To The MCU
Much of the hype for Infinity War battle scene that had "like forty superheroes." In many ways, it might seem like the X-Men are a perfect fit for this type of crossover, since the X-Men movies have been built around ensemble casts ever since the first movie released in 2000.
But whereas the Fantastic Four are in a poor position after two false-start franchises, and could greatly benefit from being absorbed and rebooted as part of the MCU, the X-Men movie franchise is doing just fine. With ten movies released so far and more on the way, the X-Men universe benefits from a straight-forward (time-travel and confused continuity notwithstanding) central trunk of team movies like Logan. There's little reason to reboot the X-Men as part of the MCU, and trying to merge the two universes would be a logistical nightmare.
More to the point, the MCU doesn't need the X-Men. While the Fantastic Four could simply be introduced as a new corner of the MCU (similar to the Captain America: Civil War, which dealt directly with the disastrous impact of super-powered people running wild in the world, made no mention of the Inhumans as a contributing factor to the Sokovia Accords.
Why the Fantastic Four Fit In The MCU Easier Than X-Men
In Marvel Comics, the X-Men have repeatedly sat out major events (like Civil War), and the question of whether they would be better off in their own universe entirely is frequently debated among fans. Some have argued that the X-Men simply don't fit, since a core part of their characterization is the fact that the world fears and hates them because of their abilities - something that doesn't quite gel with a world where kids have Captain America and Iron Man action figures.
Related: Doctor Strange & The Marvel Illuminati Explained
The main appeal of having the X-Men share a universe with the rest of Marvel's superheroes seems to be the ability to bring in individual heroes - like Wolverine and Professor X - rather them full-blown superhero team-ups. Certainly it would be fun to see Hugh Jackman's Wolverine interact with the Avengers, but the thought of him dragging the entire X-Men universe and all its complications behind him is a little exhausting. Similarly, Professor X is a founding member of the Illuminati in the comics, and so it would make sense to have him as part of the movie version as well - but it would require a considerable amount of set-up in order to make Xavier a cornerstone of the MCU.
The Fantastic Four are fondly referred to as Marvel's First Family, since they were the very first superhero team created by Stan Lee and Jack Kirby in the 1960s - predating both the Avengers and the X-Men. As the previous movie versions have demonstrated, they're also not the easiest superheroes to convincingly translate to the big screen, and they could definitely do with Marvel Studios' magic touch. In the wake of the Avengers' momentous battle with Thanos, Marvel should be looking for new heroes and new stories to explore, and the Fantastic Four are in need of a worthy movie adaptation.
Third time's the charm, right?
More: Avengers 5 Should Definitely Include The Fantastic Four