The retailer announced a variety of tablets running on Google's mobile OS are on sale at more than 1,600 of its U.S. stores, from manufacturers such as Acer, Asus and Toshiba.There are not as many games and apps for Android tablets compared to the iPad, so GameStop will pre-load a bunch of free games with each tablet sold, including Sonic CD, Riptide, a free issue of GameStop's gaming mag, Game Inf