I will just answer to your question coz I don't know how popular Mortal Combat is; I don't know so much about what's going on in the fighting action games.
One thing I'm sure is that they hardly make amine from those [media? NOT SURE AMBIGUOUS -5point] in the United States for various reasons.
The biggest reason I assume is the lack of popularily of the contents.
Compared with that, TV shows are much well known to the public more than you expect. Prison Break and 24 are the good examples of which are very popular. South Park is getting more famous.
And, Full House has many fans who enjoy the time back in the year it was released.
I don' t see any reasons why they need to make anime out of these programs.
I think animes are made out of contents which often need readers to fill and strengthen the worlds with their imaginations.
Since characters and scenes aren't static in TV programs, these kinds don't need people's hands to get animated.
Games by Bethesda are popular here, as much as Minecraft, Terraria, and etc. Many of the Japanese gamers are using Steam.