Serious games provide an opportunity for people to learn in an engaging manner. This paper investigates whether historical facts can be learned better when people are just watching a game, or actively participating in it. We further studied whether the resolution of the display and the quality of the presented graphics had any impact on learning outcomes. Thirty participants either watched or participated in two scenarios from Assassins Creed Discovery Tour, one from ancient Greece and the other from ancient Egypt. Our results show that participants who actively participated in the game had significantly better test scores results than those who simply watched the game. Display resolution and graphics quality made no significant difference to knowledge retention in our study.