Injustice was a lot better than most people give it credit for. It's not a serious bzns competitive game, and it was never meant to be, but it's a lot of fun.
Injustice is fun with some friends. I appreciated they gave you an alternative way to do moves (i.e. HCF+P rather then B,F+P). It just never replaced Capcom/Namco games as the go to fighting game for the hardcore fans.
IMO though for a second when MKII came out I think MKII was the go to game. I believe it came out when SFII 'HF was out and the masses were getting a little tired of it (at least in my community). It was still a big deal, but not as much as WW or CE.
MKX I still haven't bought yet. It looks great, but how's the online rooms? I heard they threw in GGPO so there shouldn't be bitching about netcode.