The role-playing fantasy has been a staple of electronic gaming since the 1970s, when students cobbled together interactive quests on university mainframes. However, the genre has fallen out of favor in recent years, overtaken by grittier dramas like the “Grand Theft Auto” and “Call of Duty” franchises. “Dragon Age: Origins” tries to bring some of that grit to the fantasy role-playing game. In its quasi-medieval kingdom, Ferelden, the streets are muddy and the buildings are crumbling.