Drs. Cheryl Olson and Lawrence Kutner are cofounders of the Harvard Medical School Center for Mental Health and Media. They've written a book called Grand Theft Childhood: The Surprising Truth About Violent Video Games and What Parents Can Do, based on a study of gaming in individual families. Despite what the title of the book sounds like, it's not the usual stuff about how game addiction is making kids into little sociopaths and we should protect them from it.
My takeaway from the interview is this section:
First, play games with your kids. Find things that you both can enjoy. Young teens who took our survey (and boys in focus group studies) said that they rarely played with a parent, and most would like to. I think more families are playing together now that systems such as the Wii make games more accessible to casual players. If your child is a bit older, ask him to teach you how to play a level of his favorite game. It’s a healthy thing for parent/child relationships for the child to teach the parent something for a change. It’s also a chance for parents to learn more about their child’s interests and strengths.
When you buy games, look for ones that encourage kids to plan and problem-solve (that could be Zoo Tycoon or a Legend of Zelda game). Choose some that allow for collaborative play, with you and/or with friends.
Notice how games affect your child emotionally. A lot of young teens we studied used violent games to cope with angry feelings. That’s probably healthy in moderation, but might be a problem in excess. Some teens use zombie-type games to master fears, playing over and over until they beat the game completely. If a game seems to upset your child, put it away until he’s older. Keep your games with grown-up themes or scary content someplace inaccessible, and only play them when the kids are in bed.
Don’t worry too much about how much time your child spends with games if she has at least one good friend, does well in school, takes out the trash the 3rd time you ask, etc, but be alert to signs of problems. If your child often misses sleep to play games, loses interest in other activities, or is doing poorly in school, the game play may be a problem or, it may be a symptom of another problem, such as depression, that the child is trying to cope with.
As far as I'm concerned, that's all great advice.
(Note: the preceding link is nearly a year old. Since that time, Ben's druid has reached level 45, he's specced as a spellcaster, and his damage is stacking up well against that of many random dungeon teammates.)