It all depends what you like, but I agree that Wario Ware is the ultimate in addictive time wasting games, you'll get your money's worth right there. I haven't finished it yet, but if it's your thing, the new Castlevania game is really enjoyable too, and again, if it's your thing, nintendogs is another popular epidemic.

If you want to import and can find FAQ's to combat the language barrier, there are loads of awsome games in Japan that you could get too. Anyway, get a DS, your life will be much better.