As others have already said, buying a console for one game is a pointless waste of money. But as others have also said, FFIII isn't exacly the only good game on the DS. Square Enix are supporting the DS like crazy. I mean, Dragon Quest 9 is a DS exclusive. DRAGON QUEST 9! The actual next game in the series. DS exclusive.

Plus there are all the Final Fantasy Advance games, which even though they are pretty new you could still probally buy cheap, especally 1, 2, and 4.

And then there are the SE tacktical games, such as the Cystal Cronicles game, and the Ivalice Alliance games (Final Fantasy Tacktiocs Advance 1+2, Final Fantasy XII: RE).

And yet there is more! Children of Mana! Magical Startsign. And these are just the Square games! What about Castlevania, Lunar Dragon Song, Lost in Blue, and many others that arn't RPGS!

So, to summerize, don't buy a DS for FFIII. Thats silly. Buy it for all the Square games!