PS3 Ultimate MAME Project

I'm been searching far and wide, and maybe this answer is right under my nose, but I can't for the life of me figure out how or if you can play 2 players on any of the 2 or more player games, like TMNT, Simpsons, Street Fighter etc. Has anyone had the same issue, or does anyone know how to get the second controller to register?

Thanks!

Wow nice!