The new service also will track the activities of gamers across other media platforms, including television and the Internet.
Nielsen's plan underscores the growing importance of the video game industry to advertisers, who already have their products placed in many titles, particularly those dealing with sports or set in cities.
Still, unlike television, where ratings are used to help negotiate commercial rates, the video game industry has yet to come up with standard measurements to use when buying and selling advertising space.
Nielsen's latest venture will also provide advertisers with data about the playing habits and tastes of gamers, typically the hard-to-reach young male demographic highly prized by advertisers.
The sale of video game hardware and software generates global revenues of about $30 billion a year, while advertising and brand displays have grown increasingly prevalent in the virtual landscapes inhabited by gamers.
Forecasters expect the emerging market for in-game ads to reach $1 billion to $3 billion by 2010, but that is a fraction of the more than $60 billion spent on all television advertising.
Nielsen spokeswoman Karen Gyimesi said the new video game service will build on the ratings sample the company already has in place for television, with some preliminary gaming data being made available in early 2007. But she said the full service would probably not be up and running until the middle of next year.
Nielsen, a unit of media and market research company VNU, has been measuring TV audiences since the 1940-50 broadcast season.