Do video games kill brain cells

That's an interesting question. The answer is no, they don't, but they can have other effects:

• The brains of adolescents that spent a lot of time playing video games showed greater cortical thickness in two brain areas. (Cortical thickness is good... it means greater brain density, like you are exercising that part of your brain.) That might mean that video games can improve the brain in certain ways. Other people argue that the studies only mean that other areas of the brain will remain underdeveloped. There is no way to know that because we don't know if the lack of video games would have led individuals to other brain-enhancing activities, or if the people who like video games would have chosen similar activities whether video games existed or not.
  
• Violent video games have been shown to desensitize people in some ways to real violence.
• Video games can help with depression and have been shown to help stroke victims recover.
  
• Video games, like many other activities, can be abused and become an addiction. Like other addictions, certain people seem more susceptible. Monitoring your gameplay and making sure that it isn't interfering with real world responsibilities is imperative.
• Video games can be quite effective in simulating real-world experiences. Learning how to do something difficult or how to figure things out can be learned, often in an enjoyable way, through video games. For instance, teenage gamers were better at virtual surgery than actual medical residents in one study. Video game instruction also helped dyslexic kids read better.