Reader Rabbit games are great. They range from preschool age until about 3rd or 4th grade. The games are easy to understand and well thought out. Kids love the music.
I am 27 and I loved Reading Rabbit when I was growing up. I think it is a great game because it has been around since the apple 2e. I learned to spell with it and enjoyed it. I would say anywhere between 4-10 years old is a good age.