I am trying to get into Handheld games again since the 3.D.S has got me somewhat hyped. Besides that though I was watching T.V and a Picross 3D add came on and it looked very interesting and made me want to get into handhelds agin as well. I don't know if I will get a 3.D.S yet because I want to wait until E.3. Anyway I now want to stop playing the Wii for some time(Even though I still have about 5 games that I still want to beat but haven't yet) and start playing the D.S again. So please give me some ideas of AMAZING D.S games that I would enjoy. Picross is on my mind since I like Strategy/Puzzle games but I am not 100% sure on what to get yet so please list me your favorite D.S games and explain what they are about or why I would like them.

i would recomemd :

LoZ:Phantom Hourglass/Spirit tracks. both incredible games and good for those who like zelda games. good puzzles and combat.

any of the pokemon games: good turnbased rpgs that dont get old(atleast that quickly)

New Super Mario Bros:...its 2D mario...not much else to say

Metroid Prime Hunters: probably the best fps on the DS

(some personal favorites) Moon/Dementium 2: great fps' with good action.

ill think of more later.

Well the obvious ones are: Mario Kart DS and NSMB Wii. Also check out Yoshi's Island DS if you liked the first one, or even if you like platformers.

Some other great games:

Castlevania - Order of Ecclesia - just has that old school vibe to it, and one of the few very challenging games I've played this gen. Good amount of content, even after you beat the game.
Rythm Heaven - Really fun and unique rythm game. Kinda like warioware mixed with guitar hero (the drum part)
Big Brain Academy - surprisingly fun, also very challenging, at least to earn the platnuims. Really works the brain..
Scribblenauts - Has a few flaws and akward controls at first, but I love the concept of solving puzzles by conjuring up virtually any item you want.
Animal Crossing - Really fits with the DS style of games
Clubhouse Games - lots of solid mini games
Meteos - If you like puzzle games check this one out, makes good use of the touch screen.

I hear the Dragon Quest remakes are good stuff as well if you like RPGs, but I haven't played them yet.

If you love Picross, you will love Picross 3D.

Elite Beat Agents!

Addicting as crack.

Buy a flashcart download Soma Bringer and the english translation patch. Enjoy. Oh and Castlevania: Order of Ecclessia. I love Zelda btw and Phantom Hourglass was crap. I only played a bit of Spirit Tracks but it hasn't gotten me sucked in yet. Boring actually....

Oh and N Plus. The game is amazing.

Beware people are gonna recommend a lot of Square Enix shit and shitty RPGs. Don't listen to them.

the world ends with you is a pretty sweet RPG with innovative controls i would really recommended it the controls are tailored very well to the DS

Right of the bat I would recommend the entire Castlevania trilogy of games, mainly because I just went all three of them

But there are tons of great games for the DS: Dragon Quest IV and Dragon Quest V, Mario&Luigi: Partners in Time and Mario&Luigi: Bowser's Inside Story, Megaman ZX, Megaman ZX advent, Metroid Prime Hunters, The World Ends With You, Ace Attorney: Miles Edgeworth, Phoenix Wright, Hotel Dusk, Kirby: Canvas Curse, Kirby: Ultra Superstar Saga, Final Fantasy III and Final Fantasy IV, Avalon's Code, Phantasy Star Zero, New Super Mario Bros, Mario Kart DS, Pokemon Heart Gold/Soul Silver, Kingdom Hearts 358/2 Days, Legend of Zelda: Phantom Hourglass and Legend of Zelda: The Spirit Tracks, Lunar Knights, Trauma Center: Under the Knife. 

Underlined and bolded:

Have you tried the Hard Mode Lvl.1 cap? It's pretty much one of the hardest challenges I've ever had in my entire video-gaming life. And I've went through the classics, Ghouls and Goblins, Battletoads, Contra, you name it. 
If you want a bigger challenge though, try doing that mode, and get the boss medals at the same time XD It will drive you insane, especially the last bosses. 

Mario and Luigi: Bowser's Inside Story, best DS game Ive played.