It depends if it's appropriate or not. If the game takes place in New York and you wander into Times Square I'd expect to see those huge screens flashing with the Coca-Cola logo or if we're talking a game like Forza Motorsport (which I won't play) I'd expect to see product logos plastered all over everything. However if there was a huge banner for Pepsi in the middle of, let's say Skyrim, that wouldn't work for me because it conflicts with the aesthetic of the game.