You'll need an exporter for Maya. Check out....

For Quake
https://www.quakerally.com/files/md3export.shtml

For Unreal:
https://udn.epicgames.com/Two/MayaCom...mplete_Plugins

You should probably check out Modding sites for the particular engine you want to model for. Keep in mind that you're probably not going to go directly from Maya to a game engine. More likely you'll export from Maya to an specialized editor for a particular game.