To answer your question, NSMB on DS is sort of a poor man's NSMB Wii. Same basic gameplay, but the levels are a bit uninspired compared to the Wii version, and the game is a bit shorter. However, it also much cheaper than NSMB Wii, and still a great game by its own merit. The multiplayer is the highlight of the game. It's like the equivilant to Super Mario Bros 1, while NSMB Wii is the equivilant o Super Mario 3; still a great game, but a bit more simplified from the Wii version.

Mario Kart DS is somewhat similar to the Wii version. IMO the online system is a little worse than the Wii's, while most of the levels are better on the DS version. More of a tradiional Mario Kart game obviously with traditional control.

thanks =]

Wow it'll be hard to remember most but there is undoubtedly a huge list of must-play's.

Wii: (In no particular order)
Super Mario Galaxy 2
Tatsunoko Vs Capcom
New Super Mario Bros Wii
Muramasa The Demon Blade
Okami
Zelda Twilight Princess (of course)
Little King's Story
Rayman Raving Rabbids TV Party

DS: (In no particular order)
Advance Wars Dual Strike
Animal Crossing
Chrono Trigger
Shin Megami Tensei: Devil's Survivor
Final Fantasy IV
Mario & Luigi Bowser's Inside Story & Partners in Time
Pokemon (All / Any)
Zelda: Phantom Hourglass & Spirit Tracks
Professor Layton 
The World Ends With You
Trauma Center 2: Under the Knife
GTA Chinatown Wars 

To name a few... :D

oh yeah i got mixed up

Ill just list my favorite  WiiWare titles in order

Cave Story

Lost Winds Havent got the 2nd one yet

Megaman 9-10 Only if you really liked the first Megamans

The rebirths are pretty fun- Castlevania Rebirth, Gradius Rebirth, and Contra Rebirth

Adventure Island The Begining IF you liked the old ones you should like this one.

Final Fantasy The After Years. To get all parts it is a bit pricey and unless you loved FF 2 a lot you shouldnt bother

you know i own everything FF related

i'd recommend Chocobo Dungeon for you , its great! , don't know about Crystal Bearers, the combat system is...... well there isn't any

I have Chocobos Dungeon well had I let a friend borrow it and he kinda left his wife awhile back and is MIA to all of us now

im very lazy to type so heres the wii's recommendation guide :) http://www.vgchartz.com/forum/thread.php?id=67101

Nintendo confirmed backwards compatibility last I heard.

definitely get the World Ends With You
all the castlevania games for the DS are great (portrait not so much)
Advance Wars games are good
Chrono Trigger if you haven't played it
Shin Megami Tensei: Devil's Survivor is great
Zelda: Phantom Hourglass & Spirit Tracks are good
Professor Layton I hear is brilliant
GTA Chinatown Wars can be fun
metroid prime hunters is good if you can find it and you like those games
Soul bubbles is a rather unique game
and if you like metal slug you could pick 7 up
the DS fire emblem remakes (of the japan only SNES ones) are worth a look to


committing to get all the good DS games could be very bad for your wallet BTW

de Blob (fun platformer where you go around coloring the world)
A Boy and His Blob (puzzle platformer, fun and somewhat touching)
Boom Blox Bash Party (forget the stupid name, you need to bring down blocks/destroy structures by throwing various things at them, lots of fun with friends, , you can create your own levels, lots of free levels online)
Dead Space Extraction (on rails shooter)
Endless Ocean: Blue World (immersive diving game with lots of pretty marine life, not for people who just want to shoot... though this version does have sharks that can make you loose air from your tank if you don't calm them)
LEGO Indiana Jones (Lego. Indiana Jones.)
Link's Crossbow Training (crossbow training game with the Wii zapper, very enjoyable)
Excitebots (an out of this world version of Excite Truck, bug shaped cars with crazy stunts)
Rabbids Go Home (BWAAAAA! Crazy collectathon, and you get to customize and abuse a rabbid in your wiimote to boot)
Silent Hill: Shattered Memories (not really horror by today's standards, more of a psychological thriller with great atmosphere. It bothers some that you can't fight the monsters but only [try to...] run away, I found it heart poundingly refreshing)
Wii Fit: the games are actually lots of fun!
Shaun White Snowboarding: Road Trip (you feel the wind in your hair. Get it if you have a balance board)
Wiiware: Cave Story, Lostwinds 2, Nyxquest