Game Boy, the first true handheld ever and it defined what a handheld was for. Games like Tetris and super mario land showed what for the first time was possible. it was revolutionary.

DS honestly saved Nintendo IMO (if the PSP had taken over the handheld market, it's curtains for Nintendo I think) and has the widest variety of games and best third party support.

We need pokemon, Zelda, and SSB4 on 3DS and a couple more titles and i might change my answer to it!

I agree. The good thing about Nintendo is that we can count on the release of these games. And they most probably are going to be godly^^

Especially pokemon and SSB SSB on a handheld sounds to good to be true

DS atm, but I imagine 3DS will take the spot eventually

That would be the DS, at the moment. Greatest software library for a handheld ever, in my opinion. Spent countless hours playing the mini games in Super Mario 64, playing Mario Kart DS and lots of third party titles. Prior to that I pretty much only used my handhelds as Pokémon machines (with few exceptions such as the Sonic Advance games and Toy Story Racing).

With Super Smash Bros. coming to the 3DS along with Luigi's Mansion: Dark Moon and lots of other upcoming first party titles, I would expect the 3DS to get past it eventually though. We shall see.

I choose the 3DS, frankly the DS would be the current champ, but the 3DS takes what they learned on the 3DS and improves on it, and yes it adds 3D also. It really is unfair to include the 3DS so early in its life right now, but again since the 3DS is incorporating the things that made the DS great and built on it, the 3DS should take the cake.

My vote is for the DS, but I can definitely see that changing to 3DS in the future.

My vote goes to Game Boy Advance. So many quality games on that thing and so many fond memories. But, the 3DS is slowly becoming my favorite handheld. The more titles, the higher it goes. I think by the end of 2013, it'll hit that mark.