Their style of play may be a good indicator of temperament. That same boyfriend used to do things like "playfully" bring his hand toward my face in a slapping gesture, or "playfully" reach over and pinch my thigh, or "playfully" walk past me and tug on my hair. If I spoke a word, of course I was being ridiculous because he wasn't actually causing me pain, but his actions were definitely showing hidden hostility. If that was his affection, guess how he acted toward me when he was angry. Yep.

And as for actual games, watch how they are when they're losing, or when you as their partner make a mistake. I've seen cards get thrown across the room, accompanied by loud f-bombs. Anybody over the age of four who acts that way is not relationship material.