I own a dedicated MKII and also UMK3 and MK4 pcbs. I like each game for certain reasons.
MK4 was a jump into new territory for Midway and MK. It's combo and weapon system is in fact well done imo and the game was fluid and very responsive. The Max Damage concept as a Dmg limiter was an interesting idea. Although it was a 3d game it was still had a 2d plane feel. From the extended time of development, rush to get it done, and 3d tech for Midway just not being ready didn't help this game at all and turned off many ppl.
What I dislike is what others have already said. MK4 was done on mid-era lightwave 3D, the animations seemed limited and cold besides some stuff being shared. This was shown off even more painfully when you watch the lifeless and what seemed glitchy endings when you beat the game. When MK Gold came out on consoles it just seemed like Midway didnt even care. The added characters were done half-asses and used already existing sounds and effects from MK4 and felt like what was even the fucking point.
MKII will always be my favorite out of the series. However MK4 is infact under rated due to a very well done system and game mechanic. 3D Technology and what seemed to be inexperience with that tech is what hurt MK4.
I know most people dismiss Mortal Kombat as an inferior Street Fighter/ Surperior Pit Fighter....
The series was a success and they are still really the only American Company that pulled off a successful fighting game in a dominant JP developed genre