This paper presents a generic and adaptive gamification system that can be applied to any learning environment on the Web. This proposal is based on the fact that some educational activities are less motivating than others, such as memorizing. It is thus usual that students do not use learning environments, even when they are educationally effective. Gamification is becoming a popular method to enhance the engagement of users on the Web by adding playful elements into the learning environment. However, little attention is given to individual users' preferences as players. After a state of the art on user models and adaptation, a player model and an adaptation engine are proposed to make the game elements generic and adaptive.