Two games that really stand out as advergames can be found at:
http://www.millsberry.com/
http://www.click4obama.com/
These games serve only one purpose: to get people interested in what they are selling. They are mildly entertaining, just fun enough to get people to try them long enough to get their product into their head. These advergames are fairly effective, especially with younger audiences who are more easily influenced by video games.
