Metal Gear Solid is the first game to come to mind. That game taught me about war, various firearms, DNA, nuclear weapons, the consequences of those things, and even made me feel for one of the bosses that wanted to kill me. The first one was probably the most realistic in that I could believe everything that was going on. America involvement, their reaction to things, all of it. The only other game that comes close to changing my view of the world is Telltale's The Walking Dead.