As a rule of thumb, the size and scope of stories varies between different narrative mediums. Books lie on one end of the spectrum, telling the largest scale stories and live plays sit on the other end, confined by unities of time and place. Movies lie in the middle somewhere, normally restricted by performance time but capable of jumping around in location and, as it were, leaping years at a single bound. Artistic conventions are constantly pushing the bounds of these tight definitions but, for the most part, they remain true. Each medium has numerous advantages and disadvantages, and there are different problems with going in between each pair.
Comic books seem like a natural conversion to film.
The two mediums also use two streams of sensory input, audio and visual, with a caveat, once again, that comics delivers both streams through sight. They are clearly beginning to diverge, but there are much bigger differences to come. Most of the problems come out of the delivery format. Comics exist in serial form, arriving in installments that Hollywood simply cannot mimic, even with movie franchises. Film experience is more compressed.