Cincinnati, Columbus, and Cleveland are obviously the 3 cities worth visiting.  All three have decent history, interesting museums, culture, and fun things to do.  If you like parks, museums, zoos, gardens, etc., then you will have fun in Ohio.  All of those cities have Casinos and city centers.  That said, I didn't find the night life all that great in any of them.  King's Island (an amusement park) is 20 minutes from downtown Cincinnati (probably going to close down shortly).