Here is an interesting, though barely commented on, look at the world of online gaming, specifically World of Warcraft.
I do game myself, and occasionally online with Halo 2 (though usually only when I’m with “the guys” that I play with and not on my own). But nothing compared to the level of involvement exhibited in this. I nearly did once, before college. The semi-social world (semi because there is no physical interaction that I consider to be a major part of social interaction) can be quite addicting thanks almost entirely to its anonymous nature and the complete lack of requirement on the part of the player to be anything like yourself. The ability to take your frustrations out on people you dislike via people you don’t know and will never know that it is you who would go to such lengths against a person is quite addicting. Not to mention the normal addiction that video games can offer people.
On the other hand, there is social interaction and problem solving involved in such activity. People in these games are likely using more of their brain power than the average person. As noted before, there is a great deal of benefit to getting outside. For instance, I took a nice walk tonight for about 45 minutes covering roughly 2.25 miles total (guessing that I was walking an average of 3 mph, which I believe to be a fair, but possibly high, estimate. Based on one calculator, I probably burned close to 213 calories during that time alone, was able to process some thoughts from my day, and enjoy the summer evening air (which I will soon continue to enjoy with a beer on my porch). No video game in the world right now can give me that.