-1st of all, the BLOOD that runs on the characters while having a fight. The running blood looks soooo thick & unrealistic when the camera view gets close to the hit/injured fighter.
Also, there should be a little decrease in the running blood (sometimes it's overexagerating; no human being has such amount of blood in his body). Else, make some characters run more blood than the others (exp: the Outworld fighters).

-2nd, I think it's better if every character has his own VOICE. Almost all of the males/females characters has the same voices.

-3rd It's also better if every character has his own PAUSE moves for each fighting style. Not sharing one or more pausing moves between them. Sometimes some fighting moves are also shared between the characters, not a good idea (exp: Shang Tsung & Kitana's throw).

-Finally, the very common & big mistakes are the missing multiple fatalities for each character & the Stage Fatalities.

(By the way there is a graphical error when Lee Mei turns around her opponent while using her 1st fighting style. Her head turns oppositly to her body; meaning that her head must turn with her body).