I need to clear this up right away,
Mortal Kombat vs. DC Universe is
NOT a serious fighting game. It is a good time and is very fun, but only in a button-mashing sort of way. There are combo juggles and ranges to learn and tier lists present, but it is just that most people that want this game won't care.
I feel silly trying to explain the story behind MK vs. DC, so I won't try too hard. Anyways, by some strange coincidence, Raiden and Superman produced an energy transfer of such immense power at the same time that it caused a rift in the 2 universes and a "Rage" virus has spread among the denizens of both universes as the 2 worlds merge together. I am little ashamed to admit that I know where this fits in the Mortal Kombat continuity (after MK3 but before MK4), but I haven't the slightest clue where this fits into the DC side. Part of me doesn't think that it is supposed to.
So now we have that amazing story just so we have a reason to beat each other senseless. There are 10 fighters on both factions and a boss for each side totaling 22 combatants. All of the big names are present on both sides and at least a few fan favorites to fill out the roster. In terms of the fighting system, this is essentially the same as the last three MK games with 3 new features fastened in.
The first feature that was added actually has a significant role in the main storyline of the game and that is "RAGE." Underneath each fighter's health bars is another bar that fills; if it gets full, you can enter "Rage" Mode. This new mode is a 10 second advantage that grants you enhanced strength and lets you take damage without going through any animations so you can keep your combo going.
The other 2 modes are "Test Your Might" and a "Klose Kombat" Mode. They both amount to same thing which is quick time events. Basically, you press buttons to cause more damage, but if your opponent presses the same button at the same time, they counter your attack. Unfortunately, button-mashing is the only real strategy I have found to be useful.
At the end of the fight is traditionally where you get one chance to humiliate your opponent with a Fatality. Well, since some of the heroes won't kill anyone (and to get a "T" rating), the finishing moves had to be changed. Honestly, most of them are simply boring. The heroes don't have any moves where they kill people and had to be changed to "Heroic Brutalities," but none of them feel special. There are a few standouts like The Joker's and Deathstroke's, but the series has always been known for its trademark gore and this feel like it should have been an "M" rated game.
Other than having a single player campaign for both the DC and the MK side, there is a traditional Arcade Mode, Training, and online play for those that want to get beaten by a stranger. The online is actually quite impressive. I rarely experienced any lag and matchmaking was fairly quick, so it kept the fights going. Honestly, I didn't have too many expectations going into Mortal Kombat vs. DC Universe, but I found myself impressed nearly every step of the way.