We investigate how fantasy, curiosity and challenge contribute to the user experience in multimodal dialogue computer games for preschool children. For this purpose, an on-line multimodal platform has been designed, implemented and used as a starting point to develop web-based speechenabled applications for children. Five task oriented games suitable for preschoolers have been implemented with varying levels of fantasy and curiosity elements, as well as, variable difficulty levels. Nine preschool children, ages 4-6, were asked to play these games in three sessions; in each session only one of the fantasy, curiosity or challenge factor was evaluated. Both objective and subjective criteria were used to evaluate the factors and applications. Results show that fantasy and curiosity are correlated with children’s entertainment, while the level of difficulty seems to depend on each child’s individual preferences and capabilities. In addition, high speech usage and high curiosity levels ...