Some guessing here, but:

Wii:

-Guitar Hero III - Easily 200 hours.
-Mario Kart Wii- A good 100 hours
-Zelda: TP - 65 hours
-SSB Brawl: 35 hours
-Super Mario Galaxy - about 30-40 hours (?)

DS:
-Pokemon Pearl - 375 hours
-Advance Wars: Dual Strike - 80 hours
-Advance Wars: Dark Conflict - 25 hours
-Zelda: PH - 25 hours

Wii- Medal of Honor: Heroes 2: want to say its somewhere over 200 hrs but can't confirm
DS- Pokemon Diamond: 45 hrs I think

sonic and the secret ring, like 95 hours

Wii FIT.

My piggy bank went platinum awhile back.
Anybody see what happens to it affter platinum?

Wii: Wii Music & Mario Kart Wii
DS: Mario Kart DS

Wii: SSBB and MKWii
DS: Pokemon Pear and JUS.

Given that your race count is higher than mine, I suspect you guessed rather low on MKWii, because I have not made up over 100 hours more than you on battle mode.

Wii: Wii Sports, followed closely by Brawl, Wii Music and No More Heroes

DS: Animal Crossing Wild World, Nintendogs and Wario Ware Touched

DS: Pokemon Diamond (its pokemon..you know you're going to play it for a long time =P )

SSBB.