We present joint work between the University of Innsbruck and University of Münster on targeting online games as a novel class of Grid applications, whose user community (general public) is much broader than of contemporary scientific Grids. Online games are a new, large, generic class of applications not yet studied by the Grid community, with the following distinctive features in comparison to traditional parameter studies or scientific workflows: large number of concurrent users connecting to a single application instance, frequent real-time user interactions, negotiation and enforcement of precise Quality of Service (QoS) parameters, adaptivity to changing loads and levels of user interaction, and competition-oriented interaction between users, other actors, and services. We develop a novel multi-layer, service-oriented architecture for executing online games in a distributed Grid infrastructure. Firstly, scheduling and runtime steering services assist the users in transparently connecting to game sessions while maintaining certain levels of QoS. Secondly, resource allocation, monitoring, and capacity planning services allow efficient resource management that removes the cost and scalability barriers in game hosting. Finally, a Real-Time Framework (RTF) provides the fundamental technology for scaling game sessions to an increased number and density of users through real-time protocols and a variety of parallelization and distribution techniques.