Seems like you still have a lot of reading to do
Sincerelly, the Stan Lee/ Jack Kirby years of X-Men were some of my least favourite, the writers that came after did a better job with the characters and ideas.
Either Way now that the characters are gone of the way lets go to the comics that inspired the movies.
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Day 12
The first film wasn't actually based on any single comic book, it's kind of a mesh of ideas to start the franchise with but it certainly had some inspiration from the 90s X-Men cartoon:
Bryan Singer himself saw the show before making the movie and this was one of the reasons why he began to like the X-Men and decided to make the movie.