the thing I like about Injustice is that there's always something to do, like there's the 2+hrs Story Mode, there's the Star Labs Missions which is part fight part mini challenges, and there's straight up battles. The only like negative thing I would have to say about it is the overpriced DLC, awful character DLC selections (I mean I love me some Mortal Kombat and Scorpion, but I got a DC game for a reason, and Zodd?really... just cuz of the movie....) and the usual online fighters that play cheap (but I mean that's common in any game with online mode)
That was probably more than you wanted to know, but overall I think it's a worth it fighting game to have in our repetoire, but do wait for the price drop/GOTY if money is your concern~