Tried a 4 player co-op night with one shared screen and motion controls, and it lasted about 12 minutes
Set up Family Game Night at my place in Portland last Saturday with my two brothers and my roommate, and I picked a party game that uses motion controllers so everyone could jump in fast. Big mistake. The camera kept losing the smaller players because the room light was too dim, and my brother's controller drifted so bad his guy walked into a wall the whole round. We switched to a plain 2 player fighting game after that, and suddenly everyone was having fun again. Turns out motion stuff sounds great on paper but a couch full of people plus one lamp just doesn't work, so what do you all play when the group is mixed skill and you've got exactly one good screen?
My buddy had almost the exact same thing happen at his place in Beaverton, four guys crowded around one TV and the motion game just fell apart. Two of them kept getting dropped from the camera because his living room lamp was behind the couch, and his kid brother's guy kept sliding into a corner on his own. They gave up after like 15 minutes and put on a 4 player racing game where everyone uses a normal controller, and that saved the night. His rule now is motion games only when it's just him and one other person who knows what they're doing. For mixed skill groups he swears by simple fighting games and anything turn based, since nobody has to learn much and the good players can go easy without it feeling weird.