The possible leveraging of high deployment costs, and the possibility to increase revenue have also introduced the concept of network sharing between different operators. On the other hand, the realization of a user-centric paradigm in future heterogeneous wireless networks, which implies free and automatic choice among different available wireless and mobile access networks, will revolutionize future wireless networks. For this innovative concept to materialize a paradigm shift is required from a long-term contractual based service delivery to a short-term contractual and dynamic service delivery. In this paper we formulate and compare the network-centric resource allocation and and user-centric network selection problems in a multi-operator scenario using two different flavors of game theory, namely bargaining games (for network-centric resource sharing) and multi-attribute auctions (for user-centric interface selection). We also compare the contributed solutions to one another to investigate their performance in terms of efficient resource allocation, call blocking probability, and user satisfaction.