Some good additions, but not quite good enough.
First off Williams and Sega did a good job on the Genesis version in terms of the visuals and the audio. The character design are in my opinion the best of the Genesis MK titles. In terms of audio, for the first time on an MK title for the Genesis we get to hear the fighters names announced, as well as most of the dialogue from the the arcade version.
Of course, there were also some downsides to the audio and visuals. First off, the battle zones are highly repetitive in one player mode. You will pretty much fight in the same 3-4 battle zones, which does get kind of lame after awhile. Also, the backgrounds are somewhat grainy and lacking in clear detail, which wasn't so much the case in the first two games. As for the audio, the music in MK3 STINKS, plain and simple! I guess in order to add the dialogue Sega and Williams had to sacrifice a half decent soundtrack.
In terms of gameplay, the only really cool new features are the running feature and a revamped combo engine. Other than that, the gameplay is pretty generic and doesn't really take a huge step forward in the series like MK2 did.
Overall, it's a solid game for hardcore MK fans, but don't expect the same thrills and level of replay value that made such a huge fan of the first two games.