Both of them have ace versions of mario kart, trhe DS one ebing slightly better. Other than that I have listed a few good games for each.

Wii

No More Heroes (Teen Action Game not suitable for younger kids) 

Sonic and Mario olympics (Family button basher)

Mario Party 8 (party game)

Wario Ware (Party Game)

Call of Duty 3 (shooter)

DS

Final Fantasy Crystal Chronicals (action RPG)

The world ends with you (RPG)

Nintendogs (pet sim)

Brain Training

Pokemon series (RPGs)

-Frank