Providing multimedia services in wireless networks requires maximizing the system throughput without sacrificing fairness. Previous works focus on system capacity optimization but fail to jointly ensure adequate fairness. This paper proposes a new MAC scheduling scheme which dynamically takes in consideration the QoS experienced by the mobiles and the transmission conditions in an extended cross-layer design. Based on a weighted opportunistic algorithm, our resource allocation takes a maximum advantage of multiuser diversity optimizing fairness and system throughput. This provides an efficient support of multimedia services in OFDM wireless networks. Performance evaluation shows that the proposed scheduling widely outperforms the best existing wireless OFDM based scheduling schemes.