You can check that a game is age appropriate by checking its rating. Video games are given age ratings depending on content by the Entertainment Software Rating Board (ESRB). Ratings are as follows:
Games are rated for age based the type of content it contains such as violence, language, blood, sexual, drug use and gambling. Most video game stores will verify age before selling a video game to a child, but parental supervision in purchasing is recommended. Here are some useful links for additional information. ESRB Ratings Guide; ESRB FAQ; ESRB Homepage.