Injustice: Gods Among Us helps answer some of these questions. Developed by NetherRealm Studios -- the team behind the very impressive Mortal Kombat -- Injustice pits some of the greatest heroes and villains of the DC Comics Universe against each other in grand spectacle. With powers and moves fitting for super humans and a custom story mode that's as good as Mortal Kombat's, it's one of the better fighting games of the past few years.
In Injustice: Gods Among Us, we are introduced to a Superman that just had his world rocked. Tricked by the Joker, Superman resorts to killing the Joker after the Joker destroyed Metropolis with nuclear weapons and killed Lois and their child. This leads Superman down a dark path -- one where he sets up a regime, which happens to kill anyone who opposes it. Superman has convinced the other heroes and villains to join him -- because he has the power to protect everyone and create stability and peace -- and the ones that don't must be eliminated.
Batman leads the insurgents against Superman, trying to foil the regime and bring Superman down. To help defeat Superman, heroes and villains from an alternate universe (one where the bomb didn't go off) are pulled into the other one (where the bomb did go off). This helps explain how characters can fight against their alternate selves. Now, the two sides are fighting to stop each other.
There's a lot to the story, and I would say it's right on par with the one in Mortal Kombat. NetherRealm, with the help of some DC Comics writers -- the same ones who wrote Mortal Kombat vs. DC Universe -- have created an excellent story in a fighting game. That doesn't happen often. The story mode has you play through the characters, doing a couple of fights before moving on to the next character. There are cutscenes in between that advance the story, and the transitions to the fights are seamless. That's really one of the most impressive parts -- how the fights feel totally organic. Aside from the story being great -- with BioShock Infinite-esque elements of string theory in there -- it's a nice way for you two get your hands on all of the characters in an entertaining way. And it'll only last around five to six hours.