Intelligent game-based learning environments have developed and created dynamic, effective, and engaging learning experiences, serving as a tutoring framework for students of different educational levels. Although game-based features have recently been shown to have the potential to improve intelligent tutoring systems in these learning environments, there remains some debate and challenges in terms of their benefits for learning. Therefore, in this study, we aim to identify the categories of game-based features and explore how particular game-based features influence students' learning in intelligent learning environments. To achieve this goal, we presented the findings of a systematic literature review published between 2016 and 2021. Content analysis showed that the most frequent game-based features used in intelligent game-based learning environments are incentives, personalized agents, and navigation, mostly in various combinations. Moreover, the study provided evidence that the influence of game-based features on students' learning in intelligent game-based learning environments relates to engagement, motivation, attention, enjoyment, and learning achievements. The findings provide an overview of the influences of game-based features on students' learning, which can help educators and game designers create optimized game-based features and successful intelligent game-based learning environments that have a positive influence on learning.