Effects of Game-based Learning on Motivation for Learning
I'm a higher ed instructional designer. Our industry is beginning to integrate serious games(a term that seems to be replacing educational games) and the principles of gamification into our courses, particularly those that are online. We know that K-12 students are using Learning Management Systems, mobile devices, and games to learn (whether formally or informally), so we are getting ready for them.

On gaming versus studying: A well-designed serious game and/or gameified learning environment IS studying. Instructional designers like myself who are present on a team developing a gamified online unit of instruction or course are there to ensure that pedagogical best practices are embedded in the content. I can't really answer a generalized statement about higher or lower incentives/motivation because no specific audience has been defined. Individuals, and their reaction to different types of curriculum, vary.