My biggest complaint about injustice is like some others have said there's so much safe stuff in the game. With some characters you can barely tell who is good at this game and who is just mashing buttons. I'm not saying the game has to have any high learning curve, just not have a derp special or string that is the answer for everything plus be so stupidly easy to do you can't mess it up.
In MK if someone was doing NDC's and instant gas blasts or doing Sonya combos into MS stance mix ups I knew they were competent. Anyone can press f23 and shoot lasers full screen or press b1,3 + machine gun with GL but I've seen some grand finals that pretty much look like that.
Kenshi, Sonya, Cage, Kitana etc don't have tons of safe things? Most of their important tools are safe on block and sometimes advantage on block.
Superman's Forward 2,3 is more comparable to Cage's Forward 3 pressure, which is safe and sometimes had random advantage.
I don't understand why down 4, military stance is considered to be such a huge deal...I barely played Sonya and was doing her military stance stuff when I played. It's not anymore impressive than canceling stuff in Injustice.
NDC's take the risk factor away from Kabal's nomad dash too because he doesn't have to commit to the risk.
Kenshi's super plus 8 frame spirit charge that also had armor. Sonya's ex cartwheel that was minus three that launched into reset and follow up pressure.
Sometimes if you blocked Kitana's forward 2,1 she could beat out your poke cause she'd be at advantage or only minus one.
For zoning, Cyborg's zoning would be more comparable to Kabal's zoning than superman's zoning tools.
TL;DR these games are made by the same company and they both have very safe options that are incredibly good.
It's fine if people like MK9 better, but MK9 was not too much better or different from Injustice in terms of safe, abusable tools.