Just 5 games??!?!!!!?! is almost impossible
Ok, There are a lot of good games for DS but I'm going to mention games that doesn't have the recognition they deserve. So don't expect Nintendo or Square games here
Soul Bubbles - great levels design, great music, very original and adictive
Henry Hatsworth and the puxxling adventure - fun, original and well resolved
Hotel Dusk; room 215 - carisma, mystery, great screenplay and some great puzzles
The world ends with you - a modern rpg that absolutley works!
Elite beat agents - crazy, fun and great music.
Honorable mentions: Time Hollow, Suikoden DS, Polarium, Dementium, Moon, Scribblenauts, GTA, Chinatown wars, Electropankton, Ninja Gaiden, Ace of Attorney.