I don't know all too much about fighting games, but I think Mortal Kombat would've worked if they would have added more horror & mysticism elements & upped the drama. Sure, people were getting killed & the fate of the world was at stake, but... those four main characters were rather calm about it.
OH! What would've been good too is if some of them made friends/ they formed alliances with other fighters to make it & had to watch some of those people get killed (The closest they got was hinting that Johnny felt bad for that Art guy) If they would've done this among other things to show that these characters were actively trying to take Shang Tsung down, yet have Shang use his knowledge of the rules & expertise at bending them to screw them over again & again, it would've worked very well.
Top 3 games I would like to see as movies:
UNCHARTED: Same storyline as the games, but try to tidy them up & tie the stories together better.
ASSASSIN'S CREED: Same story, but have Desmond escape before anything significant with Altair happens. Do a trilogy of films based on the three Ezio games with the Altair story being revealed to Desmond piece by piece through the bleeding effect.
TOMB RAIDER: A new story that will take the character seriously and treat her like what she is... Once again, I think I'd go to Nikita for inspiration.