Dark Superman isn't Superman.
When I saw Iron Man I was sitting there thinking "Holy shyt. Iron Man jumped out of the comicbook into this movie." Same with Cap. I never felt that I was watching THE "actual" Superman during MoS, just some alternate universe elseworlds retelling of the origin. He let his dad die. That would just never happen. He would have fought Zod without destroying Metropolis and he woulda done something besides outright murder Zod.
The main thing that throws me off about the neck snap was HE TURNED ZOD'S HEAD TOWARD THE FAMILY. This would have had the effect of moving Zod's eyes that last bit toward them and cutting them all in half. So it wasn't even organic, just shoehorned in as a reason for Dark Superman to kill a mofo.
Look at the Joker they chose. Look at the hideous Bat symbol. These people are not giving me the "real" DCU, they are just using the names to bring their vision of these characters. I'm sick of that. Just put the comics on the screen. We have like 100 years of scripts and storyboards. Just use them.
So that's why I was underwhelmed.
/nerd rage rant.