Göbel, S., Gutjahr, M., & Steinmetz, R. (2011, October). What Makes a Good Serious Game–Conceptual Approach Towards a Metadata Format for the Description and Evaluation of Serious Games. In Proceedings of the European Conference on Games Based Learning. Academic Conferences, Ltd., Reading, UK (pp. 202-210).
Here are some research papers that I believe to be important in the field:
Gee, J. P. (2008). Video games and embodiment. Games and Culture, 3(3-4), 253-263.
Calleja, G. (2007). Digital game involvement. Games and Culture, 2(3), 236-260.
Squire, K. (2006). From content to context: videogames as designed experience. Educational Researcher, 35(8), 19-29.
Clark, R. E. (2007). Learning from serious games? Educational Technology, 47, 56-59.
Gerber, S., & Logan, S. (2011). Gamers and gaming context. British Journal of Educational Technology, 42(5), 842-849.
Chee, Y. S., Loke, S. K., & Tan, E. M. (2009). Becoming citizens through game-based learning: A values-driven, process approach to citizenship education. International Journal of Gaming & Computer-Mediated Simulations, 1(2), 32-51.