People like to bet online on a wide range of sports, but certain sports and markets are the most popular year after year. The outcome of the Super Bowl is one of the most bet events in the world. So it's safe to say that soccer is the most bet on sport. However, the Super Bowl only happens once a year, whereas tennis and horse racing are played almost year-round. These sports are really popular with daily bettors. Football, the European form of soccer, is also the biggest sport in the world - billions of dollars are bet on soccer alone every year. So if you choose one of the following sports: soccer, horse racing, soccer and tennis, you are not far off.