Warning: Spoilers for Spider-Man: Brand New DayThanks to Spider-Man: Brand New Day, the Marvel Cinematic Universe has a great opportunity to improve upon the first-ever X-Men/Spider-Man storyline in the source material. Bettering the odds of that scenario is the fact that the MCU has already allowed one of its flagship X-Men characters to debut in a Spider-Man movie. Played by Sadie Sink, Jean Grey turned out to be the real force behind the threat Tom Holland's character was working to defeat in Spider-Man: Brand New Day. Spider-Man appearing in the first X-Men movie is a scenario that shouldn't be ruled out either. Regardless of when it happens, it would give Marvel a great opportunity to lean on the beautifully crafted dynamic that Peter cultivated with Jean in Spider-Man: Brand New Day.