Warning: SPOILERS for Solo: A Star Wars Story!
In Solo: A Star Wars Story, Han Solo meets his caped frenemy Lando Calrissian for the first time, but their shared history isn't quite as momentous as fans have been led to believe. In fact, like X-Men: First Class was for mutant best buddies Charles Xavier and Magneto, Solo is actually reductive to the legend of Han and Lando.
The Empire Strikes Back first introduced Lando as Han's "old buddy", though Solo had trepidation about calling upon Lando to give them sanctuary from the Empire in Cloud City on Bespin. When Chewbacca roared an objection to the idea of relying on Lando, Han replied "Well, that was a long time ago. I'm sure he's forgotten about that." What were Han and Chewie referring to? The famous sabacc game where Han won the Millennium Falcon and Han out-swindled Lando at cheating, perhaps? Or is there something more that happened later on?
The way Solo left things, it's uncertain whether Han and Lando saw each other again before the Falcon landed on Bespin over a decade later, and it doesn't matter. As things stand, they could never meet again until Empire and the story still works. Sure, there's still years of untold story that could unite them again, but if the original trilogy is anything to measure by, the most notable parts of their relationship all occurred in the first week of them meeting.
Comparatively, Professor X and Magneto have been friends far longer than Han and Lando and had much more momentous interactions in the original X-Men movies, but as X-Men: First Class depicted, the beginnings of their friendship and the amount of time they actually spent with each other was also relatively brief. The origin tale of how the two mutant leaders became the dearest of friends only spanned a few weeks, tops. First Class, like Solo, takes on the challenge of depicting an epic friendship but ends up truncating it for time.
However, Xavier and Magneto are defined by their polar opposite worldview in regards to mutants and humans co-existing, so the (far more lengthy) time they spent opposing each other is based on their philosophical differences. After First Class, a decade went by until they saw each other again in the 1973 timeline of X-Men: Days of Future Past, and again, they were only together a few days before Magneto went rogue again. It would be yet another decade before they would next meet in X-Men: Apocalypse. But that's still quite a lot more time to actually form a genuine bond than Han Solo and Lando Calrissian had.
If all fans are left with is what they saw in Ron Howard's film, then the sum total of the canonical shared history between the two smugglers was ultimately two sabacc games and completing the Kessel Run in less than 12 parsecs (if you round the number down). So the beginnings of this epic friendship really only lasted about the length of a long weekend.
Enduring friendships that began with curiously brief times actually spent together are a familiar convention in movies, but prequels like Solo and First Class somehow make them less epic than fans imagined. Still, considering the wild, life-threatening, and friendship-affirming scenarios both Han Solo/Lando Calrissian and Professor X/Magneto found themselves in, fans can buy that iron-clad bonds were forged between the duos even though the films show they spent relatively brief amounts of time together.
And, just like how Charles and Erik liked to test each other with games of chess, Han and Lando probably learned everything they need to know about each other from their sabacc games in Solo. Ultimately, it was enough to become buds for life, but fans can't be blamed if they always imagined more than what the movies show it was.