My personal thoughts on MKX are that It is a great game, with hours of fun and tons of things to do. BUT if you are not a huge fighting game person, then this may not be something you want to buy just yet at full price, but I'll write some pointers below to help your decision.
The story (which I have only played a few chapters of) seems really good and I like the direction they have gone with it (Cinematic, sometimes with button prompts, then fight, then Cinematic, then fight and so forth).
If you have friends that you'd play it with, grab a second controller and let the frustration pass between you and them as you both fight to be top, it's great!
Online is fun, they've added more to it than just "find player, fight, rank up" and rinse and repeat. They've added Factions, Towers, King of the hills, and more. Heck, they've even added a Factions Boss, which every player in your faction can go into a match with that boss and try and take as much health of it as possible, to help your faction take it down. I found that pretty cool.
Gameplay has improved from the older games, better graphics (obviously) fluid movements, it looks great in 1080p (PS4/PC only) and at 60fps, environment attacks are cool and the xrays/fatalities/faction kills and (if you can do them) brutalities are,well, VERY brutal and gory. Also test your luck and test your might return.
Krypt. Go spend points you earn in the Krypt to unlock more and more stuff. Oh and beware, things lurk in the Krypt, almost fell of my chair the first time!
There are only one thing I dislike about the game which is that you cannot have a tag match anymore, so no 4 player matches on or offline. This sucks for me because me and my girlfriend would vs my best friend and his girlfriend all of the time online on MK9.
So if you want a quick summary, its a great game, tons to do, if you love fighting games, you'll love this, otherwise I'd say rent it, try it and if you like it, buy it.
Hope that helps :) -Dane.