The Sims 2 on Nintendo DS doesn't have an ending — it's an open-ended life sim. "Winning" means achieving your self-set goals: max skills, dream home, family, career top, all aspirations complete.
Remember: The Sims 2 DS is a portable dollhouse. Set a goal (e.g., "Reach Tiki God career, build mansion, 10 grandchildren"), pursue it, then set a new one. That's the game.