I've been playing video games since I was five years old. The original Nintendo games were cartoony and in no way looked real. They were games designed for children and videogames grew as I did. By the time I was a teen, women were half naked and games were being banned for being too real and violent.
Now, I am a parent and my own children are at the age that I started playing games. They want to play my Xbox and PlayStation, but many of the games I have aren't good for kids. Gears of War, Halo and a ton of other shooters are great fun, but are incredibly bloody and have very foul language.
You're not going to see Mario saying some of the language from Gears. I let my oldest son play Halo; he's nearly seven. Halo has some blood and language, but he understands that it's just a game and that he's not supposed to say those words. My other two can play Spider-Man and other games, but nothing too violent and realistic.
The primary market for videogames these days isn't children is teens and adults. You can't read a gaming magazine without seeing a dozen games dealing with death, drugs, guns, sex and everything else I don't my five-year-old introduced to quite yet. There are several games that I own that I can't play until after my children are asleep and for good reason. Rise of Nightmares is a great Kinect workout, but they don't need to see zombies being hacked and slashed.