Kinda hard to tell because Perfect Legend plays a lot of fighting games, like almost all of them but he plays MK a lot and I believe that he was a champion in one of the DOA5 tournaments. DOA was actually where I first knew about him and I only discovered he plays MK after that Sonicfox vs Perfect Legend beef.
SonicFox, as you already know, plays and wins in almost everything... I don't know if he's chosen a specific game as a main game though....