Here you go:
The best games in my eyes are:
Hotel Dusk: It's an interactive graphic novel with puzzles. Doesn't sound like much of a game and it is mostly reading, but hey it's still one of the best experiences on the DS. I myself loved it even though I loathe reading.
Kirby Canvas Curse: This is one of the most genius uses of the touchscreen ever used. You draw lines to guide your Kirby ball throughout many awesomely deisgned levels, this game could never be done on any other system quite as effectively. It's extremely sugar coated(which isn't a bad thing), but it's definatley fun for any age of gamer.
Animal Crossing Wild World: If you're into relaxing in your games and having your own virtual life, this one is for you. It's the kind of game you have to play for awhile to get it.
Tetris DS: It's Tetris on the DS and it has online play to, it's a get.
Elite Beat Agents: A ton of popular American songs strung into one game with one game. It's a lot of fun tapping along to the beat in this one and it's an experience that could only be done of the DS.
Why some popular games are a waste of money:
Metroid Prime Hunters: It'll give you hand cramps and its single player sucks.
Mario Kart DS: Snaking is super accessable in this game therefore in order to keep up with anyone you must snake. In my honest opinion snaking isn't fun unless you only play games to win rather than to engage yourself in its good gameplay...then it'll be fun.
Starfox Command: This game is too basic for its own good, both in SP and MP. I'm sorry, but everyone on MP will do the same thing because there's not much else to do....so it's not much fun.