Digital applications are a valuable addition to traditional healthcare. An opportunity in retaining motivation to use these applications lies in gamification. To design a gamified healthcare application for a specific target group, such as the older adult, detailed insight in their game preferences is needed. This insight enables us to tailor gamification to the user to make applications more engaging and usable, which is thought to better facilitate underlying healthcare goals. This raises the need for methods to assess these game preferences. Towards such a method, we deploy a classification for game content based on the five domains of play theory. In this study, 12 older adults played five off-the-shelf tablet games for one week. Preferences were assessed through a questionnaire, log data and semi-structured interview. The resulting overview of preferences was used to make recommendations for future gamification as well as a refinement of the classification.