The fact is that video games are generally a bad thing. It is not necessary, however, to remove them from your child's life all together. Careful regulation of play time, careful monitoring of themes and content of games, and of course the perpetual struggle against obsession are all necessary.
Role Playing Games (RPGs) are now designed to have several days of play time (many in excess of 60 hours) because they are aimed at teens and adults who are willing to dedicate this amount of time. For a young child who may be interested in the game, it can be a nightmare for a game to go on for hours and hours without reaching any major plot points. These games can easily become obsessions and should be avoided.
Games that involve a lot of senseless violence or criminal behavior (WWE, the Grand Theft Auto series, and such) should be restricted to children who are 1) teenagers, and 2) have been prepared for the fact that these are fictitious games and do not apply to real life. Many parents I have helped will swear up and down that their child understands this distinction. When their child hits another child at school and says "it doesn't really hurt in my WWE video game," the parent finds out that this distinction, especially for young children on the autism spectrum, is not always clear.
For pre-teens and teens violent games should be, as often as practicable, as realistic as possible. Games like Medal of Honor and Ghost Recon, where real war scenarios are being played out are good examples. When people are shot they are hurt and they die. The connection between real violence and the real effect of violence is clear. However, I would not recommend these games to younger children on or off the spectrum. I recall that my grandfather (of blessed memory), who served in the US Army in the Pacific during WWII, once visited us for a few days. When my younger brother started playing a WWII game my grandfather's eyes were suddenly open wide and he turned pale white. He walked out of the house and started pacing back and forth. The violence was so real that he was taken back to the "killing fields of Okinawa." While I recommend these games over others because it is important to see the real cause and effect of violence, the fact is that these games are much too real.
Games where there is violence against aliens, the less human-like the better, are not as bad. Logistics games can be very useful. I recall a game I had for the Super-Nintendo (giving away my now old-age) that included six WWII battlefields in Europe. I could move regiments around, establish a long-term strategy, and had to make sure each unit had food, ammunition, fuel, and an appropriate amount of rest before being committed to action. Later, I had a game where I could design and run a roller coaster theme park. It was remarkably accurate to running a business: I had to hire and pay employees, take loans and pay them off, address costs, quality, and price... This was very useful as I studied business management and administration.
Generally video games are not a good thing, but they can have their uses.