Long, long ago, Stanley Lieber (a.k.a. Stan Lee) was sick of writing comic books. He wanted to quit his job and try something else. His wife told him "Look, why don't you just write the kind of comic book you want to write? What are they going to do, fire you?" and so Stan Lee wrote the Fantastic Four, which led to the creation of what we now call the Silver Age of comics.
Stan Lee an Jack Kirby almost single-handedly gave birth to the Silver Age and created many of the characters you are now watching in those MCU movies.
Stan & Jack created the first black superhero at a major comic book publisher (Black Panther). The two created so many firsts including the kind of diversity firsts that make me wonder why our usual white supremacist woman-hating incel friends read Marvel comic books at all. Stan created the X-Men because he was tired of coming up with new explanations for where superpowers came from and wanted to be able to say that people were simply born with their special abilities, and accidentally became Marvel comics' standard metaphor for racism/homophobia/bigotry for decades to come.
Creating the X-Men was quite possibly the most deliciously subversive thing Stan Lee did. He created a metaphor for racism that invited millions of white boys to identify with the minority victims of bigotry in a pretty profound way, and he did it not long after a huge comic book hullabaloo in the US Senate led to the creation of the Comics Code Authority. Had parents caught whiff of what he was up to in that comic book, it would have created a huge controversy. He did exactly what caused all that wailing about "but the children!" with regards to comic books in the 1950s.
Granted, it's likely that Stan Lee and Marvel did Jack Kirby wrong, but it's impossible to understate the impact Stan Lee and Jack Kirby had on the comic book industry. They whacked American popular culture with a sledgehammer and we're still feeling the reverberations all these decades later.
I'm just glad that unlike Jack Kirby, Stan Lee got to hear the praises of the world before he died.
Excelsior!*
* This is a Stan Lee frequent joke, espcially on the editorials/letters to the editor section of comic books. The joke is that he keeps using the word excelsior incorrectly, thus demonstrating that he didn't bother looking the word up in a dictionary before using it.
PS[ent]mdash[/ent]Stan Lee didn't write Deadpool, but he was kinda notorious for 4
th wall breaking and meta-narratives back in the day, so you can say Deadpool (and the X-Men comic books showing up in the Logan movie) are products of the environment Stan created.