Professor Layton is the epitome of badass.

You mean badass as in "Rated M for Mature" or just good games...?

"Professor Layton is the epitome of badass. "

I spent a lot of time playing Animal Crossing DS, but not everyone would like it.
oh and you might want to wait for the 3DS  if you want, its backward compatible so you can still play all of the old ds games .

If they still sell them, you should get a DS Lite because they're cheaper and it doesn't seem like you'd be missing out on too many compelling features. As for what you should get I'd recommend:
 
Zelda (either one)
Scribblenauts (or just wait for Super)
Castlevania: Dawn of Sorrow
Final Fantasy IV
New Super Mario Bros
Mario and Luigi: Bowser's Inside Story
Picross 3D
Metroid Prime Hunters
Star Fox Command
Mario Kart DS
Rune Factory
 
There are probably more I'm not thinking of. Oh, and the new Golden Sun will probably be pretty good.
 
Edit: Sonic Rush is also pretty good, but I'm hesitant to recommend it because a lot of people seem to hate Sonic in all of his forms these days.

Well if you only want to play retail games just get a DS Lite - cheap and reliable. 
The XL will fit you better if you don't plan on playing the DS outside of your home.
The DSi adds an online shop w/ mini games and a camera - are you really gonna use that stuff? 
 
Games:

• Dragon Quest IX - Just do it.
•  Pokemon (Platinum/Silver/Gold or wait for Black and White) - a staple of Nintendo hand-helds, you should own at least one while you own a DS.
• GTA Chinatown Wars - nice throw back to GTA, GTA II and GTA London with decent touch screen support although swapping between regular and stylus controls so frequently can get ... tedious
• Zelda The Phantom Hourglass (and I assume that Train one too, but never played it) - Solid entry in the Zelda series that's completely controlled via the touch screen, and it works amazingly.
• The Mario and Luigi RPGs are also a lot of fun, battles use an interactive spin on turn based combat.
• Phoenix Wright Series - some of the funniest and most entertaining games you'll ever play, don't question it, at least get the first one (gonna be dirt cheap by now). 

Henry Hatsworth's Puzzling Adventure is great. It's very overlooked, I think.

Thanks for the responses. Can anyone tell me if Shin Megami Tensei: Devil Summoner is any good?

" Thanks for the responses. Can anyone tell me if Shin Megami Tensei: Devil Summoner is any good? "

" @natetodamax said:

" Thanks for the responses. Can anyone tell me if Shin Megami Tensei: Devil Summoner is any good? "

it's devil survivor actually, and it is fantastic.  Strange Journey is also really good too, but they're totally different games. "

Devil Survivor is an RPG/Strategy game, I don't know if that's what you like or not. Strange Journey is good too, but it's an old-school style RPG, with a first person views and random encounters. It's probably the hardest SMT game I've played. I also reccomend Bangai-O spirits.

Well theres yer problem. Your'e looking for good DS games at Walmart. Online all the way baby! Oh and I suggest Mario and Luigi 3. And Sonic Rush Adventure. great games.

" Devil Survivor is an RPG/Strategy game, I don't know if that's what you like or not. Strange Journey is good too, but it's an old-school style RPG, with a first person views and random encounters. It's probably the hardest SMT game I've played. I also reccomend Bangai-O spirits. "

" @SpiralStairs said:

" Devil Survivor is an RPG/Strategy game, I don't know if that's what you like or not. Strange Journey is good too, but it's an old-school style RPG, with a first person views and random encounters. It's probably the hardest SMT game I've played. I also reccomend Bangai-O spirits. "

so you haven't played nocturne then? That one does not fuck around "

Picross 3D runs so deep, so deep, it put my ass to sleep

Look for Elite Beat Agents.

Etrian Odyssey II, that game will chew you up and spit you out and you will come crawling back for more. 
 
God I love that game.

" Henry Hatsworth's Puzzling Adventure is great. It's very overlooked, I think. "

Well there is a new Dragon Quest, if that's your thing.  
 
And yeah, Devil Survivor's pretty good, but it can be tough if you're never played SMT games before. You can always ease yourself in with Persona games though! 
 
Oh, and buy an XL. They're awesome, and when you get used to them, you actually laugh when you see other DSs. They're so tiny, and... they just look like a toy in comparison. The resolution stuff isn't an issue, either. Games look real good on it. I just with I didn't have to bother with the DSi's dumb features. A 160-180$ giant DS lite shaped handheld woulda been better even.  DSiWare is useless, and I've taken like... 3 photos with the camera. It's junk. 

Taiko no Tatsujin FTW!!!! :D