I think both the X-Men and MCU movies should qualify as sci-fi. How can they not? Just because they take place in the present day? Kor
The X-Men movie franchise, like the MCU and the DCEU, belong to the superhero comic book genre and not science fiction. Buck Rogers, Flash Gordon, Dan Dare, Valérian and Laureline, etc, are science fiction comics. IMO Doctor Who, Planet of the Apes and the Alien/Predator/AvP/Prometheus franchise are viable contenders for the third greatest science fiction franchise.