I know you already gave your speech, but this is an interesting topic for me. Video games are a mixed blessing, very solidly.
I do not believe violent video games cause an increase in aggression in the people who play them often. What I do believe is that they are generally a solitary activity which, if played a lot during the formative years, can result in reduced social skills, general awkwardness and a feeling of ostracism. Of course, being a dedicated bookworm through my formative years - and well into high school - I am well aware that it isn't the only thing that can result in these traits. Only one of them. There is also the fact that multiplayer video games exist and can somewhat mitigate this trend, although that causes some of its own problems re: conflict resolution and sharing. Remember the squared-off edges of the original NES controllers? My oldest (younger) brother and I used to beat each other with them over whose turn it was.
It is a great outlet for aggression. If I've had a difficult time with something, it's cathartic to go on games and shoot the crap out of something for a while. However, it's often more cathartic (for me) to grab my sneaks and go for a good run. When I lived in an apartment complex with a pool, going for a good swim was fantastic. And if I felt un-productive, or like I was failing at something, taking some of the weighted pool toys and diving after them was a good way to get an easy sense of accomplishment. So while games are good for some aggression, they should not be relied on as the only outlet.
Do they encourage dependence? They certainly do... but so does everything else. I have an ex who developed an MMO-dependence. I also have a friend who developed a dependence on weed. I have another friend who really, really seems to be unnaturally fond of his television. And one of my relatives has described behaviours in his girlfriend that make me think she has become dependent on (and possibly also addicted to, since there's a chemical element) exercise. Anything that makes you feel good can cause dependence.
What it boils down to is parenting initially, and people who care about you once you're an adult. In your formative years, you must be taught to seek many, varied ways to vent your frustration. You must be taught that cookies are a sometimes food (even if I resent the fact that the cookie monster is used to teach it). You must be taught that sharing is just something we do, and all play and no work makes Jack a lonely boy in the long run. If you are sliding into unhealthy behaviours as an adult, someone will need to take you by the hand and discuss them with you.
Either way, the blame does not rest on exercise, or sports (which seems to send the parents into a rage more than the children, these days), or video games, or candy, or McDonald's. The blame rests on the parents, and in part on genetics. More and more, contemporary science is learning that while we may be born with certain genetic characteristics, those characteristics may remain dormant in our genes for our whole lives. We may have the gene that makes us a psycho serial killer, but perhaps we have parents who are attentive, consistent, and overall make us feel loved ... so the conditions are never right for that gene to activate and begin producing anything. It's called nature via nurture, and if you think about it, it makes a whole lot of sense.
... that was longer than I initially intended.