two top games that my little'un enjoys - both usability and longevity wise!
maisy's playhouse by http://www.simonandschuster.com/ and green eggs and ham (by Broderbund) - one of the great things about both titles is the audio which is subtle and tuneful enough to be repeated over and over again but to not become really anoying) - another is that you do not have to click and drag! - this is something that small children find pretty hard to begin with...