Digital game-based learning (DGBL) aims to harness the intrinsically motivating nature of video games to increase engagement in education. The rising field of DGBL research has consistently shown increased knowledge acquisition for DGBL compared to traditional teaching methods. However, concerns about the methodological rigor of the research have been issued. In the current work, we aimed to synthesize and evaluate the literature on primary and secondary education to identify and address the current state of knowledge and issues in the field. First, we aimed to synthesize the effectiveness in knowledge acquisition and engagement of DGBL compared to traditional teaching methods. We specifically synthesized motivational outcomes to address the claim that DGBL enhances knowledge acquisition through increased motivation. Second, we systematically evaluated the included studies on critical methodological aspects to identify current issues and provide a measure to qualify the findings of knowledge acquisition and motivation. Studies consistently showed DGBL to be more effective than traditional teaching methods in promoting knowledge acquisition. However, we found high heterogeneity in methodological rigor, with only a quarter of the studies displaying high-quality evidence. Furthermore, only three of the 23 studies measured motivational outcomes. In conclusion, we comprehensively identified methodological shortcomings in the literature, such as lack of transparency, and proposed guidelines for future research to increase the validity of findings and advance the field.