When I watched 
X-Men: Days of Future Past, I realized that one of my 
favorite things about these characters is that they are allowed to be 
imperfect and unfinished. They make poor decisions. They're selfish and 
stubborn. They lie. But they also change, and we get to see the whole 
process.
Other superhero movies give us an origin story or a full-blown hero, but
 not many deal with the hero's uncertainty as the main story. 
Uncertainty comes as a brief scene or it's used as an excuse to see the 
hero act out of character. But it's rare that we see uncertainty used 
for character development and executed well.
Days of Future Past shows us a young Charles who gives up his 
ability because he doesn't want to cope with other people's pain in his 
head.
We see a young Magneto who chooses to act in ways that benefit the 
mutant community as a whole, over and over, even if it means killing a 
friend (Raven). Nothing is personal with him—it's only mutant or human.
But then we see Charles accept that he needs to open his mind in order 
to save others, and that allows him to grow into the mentor/leader that 
is so calm and assertive in the future, even when all odds are against 
him. We see an older Magneto in the future fight to protect his friends 
with little concern for himself, even missing a piece of shrapnel that 
ends up fatally wounding him, because he was more concerned with saving 
the others.
Besides seeing these characters develop and change over time, I also love 
that we see them lose control of their abilities or be 
afraid of what they can do.
Too often in superhero movies, we're given the over-confident hero who 
always knows what to do. Or at least, he tries his best and gets lucky.
In 
Days of Future Past, though, the character don't always know what they're doing.
When Magneto is drowning in the fountain, all the cars on the street shift and tilt 
toward him. It isn't because he was going to use them, but because he 
was in danger and freaking out—so his powers went haywire.
Charles's abilities go out of control too. When he puts on Cerebro, he 
says "these are muscles I haven't stretched in a long time," meaning maybe he will have trouble operating Cerebro, but he ends up shorting 
out the machine. Part of that might have been his nervousness, but it 
seemed like he underestimated his power and then used too much.
I like watching characters who don't fully know themselves and can't 
fully control their abilities. It's so much better than a story about a 
static, finished hero.