Accurate and real-time localization independent of environment and conditions is essential for position-based vehicular applications and autonomous driving. The typical method for land-vehicle localization inevitably relies on global navigation satellite systems(GNSS), such as global positioning system(GPS) and BeiDou navigation satellite system(BDS). As the inevitable blockages, we often fusion it with other in-vehicle sensors (e.g., inertial or visual) to guarantee position accuracy. Nevertheless, it is hard to obtain high-quality observations from these vehicle-level sensors, which affects the localization performance. Recently, following the improvement of 5G technology and wide-area infrastructure, 5G/GNSS integrated localization has progressively become the main solution for high-precision vehicle positioning. However, there is no comprehensive review paper regarding vehicle localization based on the fusion of 5G and GNSS. Accordingly, this paper reviews the state-of-the-art 5G/GNSS fusion localization in vehicular realm from the aspects of accuracy, robustness, real-time security, etc., and discusses the research gaps and future research directions.