This is one of the most popular types of sites for kids, teens, and young adults because they get to give their opinions (which many kids don't get to do enough of at home, according to them) and they get to talk to others.
     So, if you want to run this kind of site, bear your target market in mind. It's worth paying a few bucks to a freelance writer or graphic artist to come up with fun games that are constantly changing, or new pools, since people will come back time and again to give their opinions. And don't forget surveys-people love to take surveys.