If you speak Spanish or French, I strongly suggest Pequeños Detectives de Monstres / Petits Détectives de Monstres. Played it with 4 year olds, it's great, collaborative, non-violent (the only enemy is the Fear of Monsters), has a little song, encourages to use physical accessories to represent in-game objects, etc. It's also designed to be played along older siblings.

Oh, and finally, game sessions last only about 15 minutes, which fits within the attention span of children.