Some games that haven't been mentioned and that are really great are: Hotel Dusk : Room 215, and Contra 4, but i doubt they'll appeal to your little sister :P
-- Live only for tomorrow, and you will have a lot of empty yesterdays today--
Tavin: "Old school megaman is THE BEST megaman" courtesy of fkusumot :)
My mind has changed. My strength has not. Kamahl, Fist of Krosa