Multimedia software is designed to allow your PC to act and appear as a home theater system (htpc), like a game frontend does. These Multimedia software is basically controlled by using a remote controller, rather than arcade controller. But Some software is remappable and can been used like that.
I have seen some plugins to some software, wich can run these game, like a FE. There are even some game launcer wich is good to start from a HTPC software. GameEX is example designed to run from a MCE, but MCE is not required to do that.
Below is a brief list of MultiMedia software, wich you can use on a HTPC projects: