I reckon the best DS game to get is Zookeeper.
No other games can match it for playability and addictiveness.
( Megalowho? feeds beefburgers to swans, Fri 26 Aug 2005, 23:55, archived)

care to explain a little about it?
:)
( zedd, Sat 27 Aug 2005, 0:00, archived)

You can play a version of it
here.

I feel the DS version is much more playable than the version above, with touch screen/stylus control a joy to use. There's a few sub-game versions of zookeeper with it too, which add to the variety. If you're able to find a way to try before you buy, you can see if it's your type of game, and whether you find it addictive or not.
( Megalowho? feeds beefburgers to swans, Sat 27 Aug 2005, 0:07, archived)