My cousin has lost an arm about 10 years ago and now beats me at every single game he owns on ps3, using the standard controller. For some games he'll use his feet for the triggers, but other than that, he just plays with one hand over the controller, and has gotten really good at it.

Looking for alternative controllers might be nice, finding some way to make do with the standard one could also help him gain more agility with the one hand he has left, which will be useful for many other things in his life.