I am attaching empirical results about the impact of games on learning. This is where empirical evidence trumps "common sense" it is not motivation. Instead it is combining traditional and game based instruction, group work and multiple sessions. A good preview to Jim Gee's visit to UNL on Aug 20th and his talk on Gaming in Education.
A meta-analysis of the cognitive and motivational effects of serious games.
By Wouters, Pieter; van Nimwegen, Christof; van Oostendorp, Herre; van der Spek, Erik D.
Journal of Educational Psychology, Vol 105(2), May 2013, 249-265.
It is assumed that serious games influences learning in 2 ways, by changing cognitive processes and by affecting motivation. However, until now research has shown little evidence for these assumptions. We used meta-analytic techniques to investigate whether serious games are more effective in terms of learning and more motivating than conventional instruction methods (learning: k = 77, N 5,547; motivation: k = 31, N 2,216). Consistent with our hypotheses, serious games were found to be more effective in terms of learning (d= 0.29, p < .01) and retention (d = 0.36, p < .01), but they were not more motivating (d = 0.26, p > .05) than conventional instruction methods. Additional moderator analyses on the learning effects revealed that learners in serious games learned more, relative to those taught with conventional instruction methods, when the game was supplemented with other instruction methods, when multiple training sessions were involved, and when players worked in groups. (PsycINFO Database Record (c) 2013 APA, all rights reserved)