Easy game (or not really game). No idea if this will work lol.
1) Look at the collection of the person who made the last post. (Click the pinball icon near their username and find the games they own)
2) Pick one game from their current collection and say something about it. Examples: Why it's the best game they own... Why you love it... Why you hate it... whatever!
* if the person who posted before you has nothing go to the last person who posted who has stuff in their collection