If you paid the original price for the 3DS you're entitled to a few free games, including some of the best the GBA had to offer.
It's a bummer when the price of something you want drops right after you buy it. If you picked up a 3DS at launch or otherwise paid more than the current sale price, Nintendo wants to help make things right. They're not giving you your money back, but they are giving you some free games.
The company already put out 10 completely free NES games for those owners, but as of last Friday, the promised 10 GBA games are now live. If you connected your 3DS to the internet and either updated the system or visited the eShop, you're automatically registered for what Nintendo calls "The Ambassador Program."
There are ten Game Boy Advance games included in all, but the standouts are titles like 'Mario vs Donkey Kong,' 'Metroid Fusion,' 'Mario Kart Super Circuit' and 'The Legend of Zelda: The Minish Cap.'
Source: Gamer's Hub