In routing design in sensor networks, reliability and energy-efficiency are two important but conflicting performance metrics. To better reconcile the two metrics for different packet delivery requirements, utility model in economics is introduced, to integrate the cost and reliability metrics in a unified framework to evaluate the optimality of the routing decisions. This paper simultaneously optimize the transmission power in physical layer, the maximum retry count in MAC layer and the routing decisions in network layer using the framework provided by the utility model to achieve the objective of maximizing the expected utility of packet delivery. In the process, packets of different importance are delivered through different routing paths with different transmission powers and retry counts in each hop. Simulation results show that our cross-layer-optimized routing strategy performs better than those with fixed transmission power and fixed retry count. It also makes a good tradeoff among reliability, energy cost and the transmission priority.