....my 5 year old (yes I know she is young for a nintendo ds lite but it was invaluable on a 7 hour flight recently) enjoys:
"Interactive storybook ds series 1" - this has a magic harp which you can compose and play music back on, a drawing tool, a colouring section, a simple counting game and interactive stories
Also, Bratz Ponyz - put aside for a moment any aversion to bratz dolls, these are cute inoffensive ponies and you get to wash their manes, powder their faces, make necklaces for them etc (in preparation for a pony beauty pageant - cynics can go and hurl outside of the room please)
What games can you personally recommend which aren't too complex?