This game does not get the respect it deserves because of fanboys pleading for gore.
-A return to a 2D fighting system, not the side-stepping 3D system (which was done well in MKA for the Wii, in my opinion)
-A very intense and challenging combo system
-Story developments
-Gore
Oh, scratch that last one. Yes, this is the main reason everyone is all in a hissy fit: MK vs DCU lacks gore in the campy, silly, over the top sense of the word. The gore in MK vs DCU is pretty mild indeed... the amount of blood spilled in a battle is more than acceptable, but the fatalities are indeed "weak". Yet, if you can get past that and accept that this is still a very intense 2D fighter with incredible mechanics, you'll enjoy yourself.
There are two kinds of MK fans: the ones who love MK for what it is as a series and as a fighting game... these are the ones who learned all the combos and begged their parents to let them buy the MK games on the 2D consoles, and people who spent quarter after quarter mastering the game at the arcade growing up. And then there are the people who just associate MK with excessive gore and don't really care about the gameplay or mastering the game.
For those who slam the 3D MK games, I can show you videos of people who have taken those games to a level far beyond what anyone thought it could be taken to. And even though this game is 2D again and has a throwback, detailed, sexy combo system, it has met with no shortage of haters. Why?
Because, sadly, many MK fans are of the latter type mentioned. They only care about the gore, they aren't real fighting game fans.
People also claim this game sucked.
Not true. It received "Good" reviews all around and was only bogged down by some cheap moves which made online play irritating (Superman, I'm looking at you). If you play with the pros, you'll notice that there is a depth to this game that may very well be unprecedented in a fighting game, in terms of combos.
http://www.youtube.com/watch?v=iLMdj3uqpfk Here is an example of what a skilled player can do with this game. You can find this kind of video available for virtually any character in the game, and the game itself features a combo challenge which is in and of itself quite challenging, even for fighting game veterans.
The game is a little too hardcore, and not gory enough, to serve MK's fanbase. Luckily, it still has sold 2 million copies to date, and gave Midway (now Netherrealm) the money it needed to start MK9.
A word about the story: The story mode in MK vs DC is a strong point, and has been widely hailed by critics everywhere as fun. Although it's silly, it works, and it does in fact make sense suddenly why the Joker can fight Superman blow-for-blow. Relax, DC has done far worse to nerf the big blue boy scout in their own publications. You will definitely have fun with the story mode. It's funny and interesting, and you can play it from two different perspectives: MK or DC.
The other great thing about MKvDC is it tries things. The Klose Kombat, Freefall Kombat, and Test Your Might sections of the battles are all fun and engaging, but tend to be underused in multiplayer matches. The best thing is the RAGE bar, which adds more strategy to the match, in that sometimes you need to make snap decisions between taking a beating and using the resulting damage to bust into RAGE Mode so your combos can't be interrupted, or using one RAGE bar to interrupt the beating being bestowed upon you.
The game is amazing. It's incredible. To say it's underrated is to say the painfully obvious to those who have ever tried it seriously. It was the #6 most rented game in 2009, by the way. If you go online today, you will still see dozens, maybe hundreds on the weekend, looking for an opponent.
MK vs. DC is a triumph of American developers, once again, over the cookie-cutter boring cinematic combos and special moves of Japanese fighting games, which have all been SF2 clones since the mid-nineties anyway. Screw those boring ***-games and those loyal to them, support Western ingenuity. FACT: This game rocks the HELL out of SF4 Sunday through Saturday.
REPRESENT, true MK fans!