Yup, that sounds right. That would be the range to cover the NES, PlayStation, & Wii/Xbox 360 generations. It's also the age range that marks the perfect intersection of youthful free time with adult-level income status. In other words, it's when most people have both the money & the time to indulge their hobbies.
Of course there's gamers of all ages- if there wasn't a viable market, we wouldn't make preschool level games or oversized handhelds to support failing eyes. But, the way our society is structured lends that particular age group a lot more leverage in their entertainment dollar. I wouldn't be surprised to learn that's also the average age for people attending movies, concerts, sporting events and theme parks.