The deployment of fifth-generation (5G) communication systems has transformed wireless communications by providing ultra-high data rates, ultra-low latency, massive connectivity, and improved spectrum efficiency. These capabilities have accelerated the development of smart cities, intelligent transportation systems, industrial automation, Internet of Things (IoT) applications, and real-time digital services. Despite these advancements, the performance of 5G networks in dense urban environments remains affected by challenges such as severe signal attenuation, multipath propagation, building penetration losses, network congestion, and interference resulting from high user density. Consequently, evaluating the operational performance of 5G communication systems under urban deployment conditions has become essential for optimizing network planning and improving service quality. This study presents a comprehensive review and performance analysis of 5G communication systems in urban environments by examining enabling technologies including Massive Multiple-Input Multiple-Output (Massive MIMO), millimeter-wave (mmWave) communication, beamforming, network slicing, and small-cell deployment. Recent empirical studies and international standards are synthesized to evaluate their influence on throughput, latency, coverage, spectral efficiency, energy efficiency, and Quality of Service (QoS). The review demonstrates that although 5G significantly outperforms previous mobile generations, optimal urban performance depends on intelligent network design, dense infrastructure deployment, adaptive resource allocation, and artificial intelligence-enabled network optimization. The study further identifies current implementation challenges and discusses emerging technologies that will support future enhancements in urban wireless communication systems. The findings provide useful insights for researchers, network operators, policymakers, and telecommunications engineers involved in the planning and deployment of resilient and high-performance 5G networks.