I wouldn't say garbage, but 3 was definitely a step back. Still an average fighting game of the era, not bad and better than many competitors, but compared to MK2 it's ass, and I was disappointed with it at the time. Over the years I've come to appreciate it a bit more though.
Ha! That's the only one I like to revisit nowadays. The first two, while I enjoyed them at the time, play like crap to me when I revisit them. I really dig the third one though. It's different that it's part beat em up/part shooter, and the whole jungle/warzone atmosphere is more fully realized graphically. I still play the NES port sometimes.