You might have heard of this app called Scribblenauts Remix.  The object of the game is for Maxwell to get a starlite.  To get a starlite he has to solve a problem.  This is where a child needs to be creative and to use literacy skills to read the problem and to type the word or words to solve the problem.  In some levels, the child has to use adjectives.  I am not sure if this app can be classified as a strictly educational game, but it is highly motivating to apply the literacy skills and problem solving/critical thinking that a child is learning in an engaging and non threatening context.  I am sure that the child is not even aware that he/she is learning when this game is being played!