***SPOILERS for MAN OF STEEL***
I was born in 1990. Do the math.
As a kid I watched both of the DC animated Batman/Superman shows (albeit Batman more than Superman) and read a handful of their titles as I got older (I'm not a die hard fan so don't try and test my knowledge because you'll undoubtedly stump me).
So, why am I telling you this? Who cares? Just bare with me for a little bit longer.
It was somehow unanimously decided among my elementary school friends that Batman was much cooler than Superman. Batman appealed to our 8 year old mentalities because he was dark, mysterious and struck fear into the hearts of criminals.
Superman was/is clearly stronger than Batman but no one seemed to take this into account when choosing the preferred hero. Why? Because even as kids everyone knew that in addition to having an image designed for the 1940's (which, lets face it, does not translate well into other decades), Superman appears to be a big pussy. Sure, he can go toe to toe with the strongest DC villains but there is nothing menacing or intimidating about him. There's no edge. That doesn't mean superheroes have to be "ooh edgy" to be compelling but in Superman's case it was like seeing your uncle fly around in blue tights and a cape. And every kid I knew essentially agreed that Superman was simply not cool.
This is obviously a childish and surface level opinion of an 8 year old, upon reading more comics I soon grew out of this mentality and developed a great deal of fascination with the character. But for most of my generation and the ones that followed, this unflattering image of the man of steel is still around.
So let's tie this into the present: Man of Steel. Not a perfect film by any means. The fight scenes, my god. They went on for WAY too long, and the Christ allegories were a bit much. We get to the climax where Superman has Zod in a headlock. Zod is hell bent on harming innocent civilians and it is clear he is not going to stop anytime soon, so Superman surprises everyone and snaps his neck.
I'll be honest, that was pretty surprising. I mean, it's Superman, not The Punisher. But Synder (and believe me, I am not this guy's biggest fan) decided to take a risk and have Superman do the one thing he must never do. After letting the shock factor sink in, I have to admit that it was a big risk which I think they handled well. What were they going to do, handcuff him and toss him into jail? "Now now Zoddie boy, don't do it again!" How else could he logically stop a being whose power essentially matched his own WITHOUT Kryptonite?
We see this problem occur over and over in the comics. Batman locks up the Joker; Joker escapes and kills 3 dozen more people when common sense dictates that the most effective solution would be to kill/lobotmize him (which most of you know was done in the animated Justice League series). So they decided to have our hero do the unthinkable and divert from the traditional image of the character.
Does this mean Superman will kill all of his enemies from here on out? Of course not. But at least it will show a new generation of fans that when faced with an unstoppable enemy, Superman will do what is right instead of chucking him off to jail just so they can break out again. And let's be honest, the real reason why Batman/Superman haven't murdered their arch rivals is because keeping the characters alive will sell future issues, it is not solely because of the hero's sense of morality.
This is not Christopher Reeve/Richard Donner's Superman. This Superman is a lot more angsty and cold, and at times a little hard to identify with (is it me or did it feel like he had some form of autism at times?) Maybe it doesn't line up with the classic Superman model that you grew up with but does that always have to be a bad thing? I would suggest taking off the nostalgia goggles that you view the character in and think about this "issue" logically..