It's most obvious impact is that video games really aren't productive, nor do they make their users better people at the end of the day. When people work, socialize, exercise, or read, they do something which helps them become better than they were when they woke up. Surfing the internet isn't exactly a way you improve yourself, but there are times when you expand your mind by reading through the news, or other topics.
Video games are not healthful in any respect. You can play with a friend, which may help you socially, but you are sitting and only exercising your thumbs. You don't really expand your mind, you neglect other obligations, and you get depressed when you do it all the time. The average person watches tens of thousands of hours of TV over their lives, but video games are just as bad. I have trouble thinking of how much you lose when you spend only one a day playing, but some do it for many hours each day.
I know that people get easy pleasure from addicting games, but there is only so far that goes before you really get depressed. When you play the same thing again and again, it gets monotonous. It may be challenging, but you don't learn new skills, get in a grey area that isn't activity or rest. It may be fun, but they only can go so far before you start feeling the impact on your normal life. They are harmful if people let themselves become obsessed with games.