The Good: Great graphics, smooth controls, gory and brutal Fatalities, well balanced
The Bad: Weak roster, awkward animations, weapons still feel kind of useless
Mortal Kombat 4 was probably the most carefully watched game in the series due to abandoning the 2D root and going for 3D. No one knew what was going to happen to the series, and a lot of fans lost hope thinking the silky smooth controls, and excellent digitized graphics would go by the wayside in 3D. However, the game featured excellent visuals (for the time) and the silky smooth controls stayed despite some slippery and awkward animations. The fourth game also introduced some new characters who I thought were some of the weakest in the series. So despite the weaker roster we got some pretty good Fatalities, and excellent stages to fight in.
The new characters like Kai, Jarek, Fujin (a weak attempt at making another Raiden), and Tanya were pretty "bleh". They didn't have that impact that the classic characters did, but some returned like Scorpion and Sub-Zero, Sonya, and Johnny Cage came back for the first time since MK2. The run button and combos were carried over into 3D which were smooth as well as a first stab at moving in a 3D environment. You would hit a button to kind of strafe to the side to avoid attacks and this added a whole new level of strategy. Weapons were introduced in free form now and every character had one. Get hit though and you lose the weapon until you can pick it back up.
The fatalities were extremely brutal and some of the best the series has seen and looked even better in 3D. This leads to a new level of detail and creativity that can't be done in 2D. This was also the slow departure from other "-alities" and the series stuck with just Fatalities. A new boss was introduced as Shinnok and Goro returned as the mini-boss. The game carries over a lot of elements that make it still feel classic, but then injects some new stuff as well. I really felt the game was well balanced and was exactly what the first MK in 3D should be. Overall MK4 is a classic and did an amazing job of transferring over into 3D which was very difficult. This of course paved a path for all future MK games, but we can always look back on MK4 as the child.