This is MK at its best, its what all of us MK fans, and beat em'up fans have been waiting for.
They have gone back to the games roots, a 2d fgihting plain making every move effective, unlike previous titles.
There are 3 areas to look at
1) Arcade Ladder- This is the basic arcade mode, defeat 10 opponents and you win the tournament and get a video. This mode is the same as it has always been. There is one bonus which MK fans will love, and that is the difficulty settings actually vary hugely. On begginer, Shao Kahn is as harmless as a puppy, on hard... Forget about it.
2) Story mode- This is awesome, the most in depth story ever in a fighting game. The best bit? You only do proper fights, none of this run around with 2 punches and kicks rubbish. It pretty much re-tells the story from MK1-MK3 with very minor changes. It poses some hard tasks such as taking on two boss characters by your self, up to defeating Shao Kahn himself, all of which are amazing.
3) The challenge tower- this is fairly easy up to the 200th challenge mark, where it becomes insane. There are old challenges like test your might/sight aswell as strike and luck. Test your luck is a randomly generated game from a slot machine. For example, it chooses first your opponent, then up to four random abilities, such as armless, headless, dark, rainbow, vampire, boosted strength/ health and many others, sometimes it will benefit you, sometimes it will make it imposible. Not having arms or your head can make it very difficult when you only have kick moves. This will take you roughly 10 hours alone, depending on your skill.
There is only one criticism I have of this game, and that is that some fighters are not very well balanced.
For example, Lui Kang has two easy combos, XXX and AAB, the trouble is, he has an attack for foward X and forward A which means you can't be moving forwards to do them, which can mean your opponent can open up some distance and you will miss, leaving you open. And Johnny Cage's X-Ray move is a Parry, and they have to hit you or it won't work. And some characters X-Rays have to be activated right on your opponent and others go the whole length of the screen. This sucks, but you get used to it.
All in all a very solid game, not just one of the best fighting games this year, but a definite contender for best game of 2011
P.S. from the ending its very clear that there is going to be a follow up.