Big games for DS at TGS:
-Nintendo:
Ash: Archaic Sealed Heat
Diddy Kong Racing DS (not released in Japan yet)
Mario Party DS
Mario & Sonic at the Olympics (counts for Wii as well)
and hopefully some new game anouncements, as they often anounce a bunch of new stuff at their private show
-Square Enix:
DQIX (the king of the show, and as soon as you get in the area you can play the demo with download and play)
FFIV
FF:CC: RoF
It's a Wonderful World (this one is going to be huge)
-Konami:
Contra 4 (I'm not actually sure how big Contra is in Japan...)
Vandal Hearts
-Capcom:
Phoenix Wright 5 (whatever it is in Japanese hehe)
-Sega:
Mario & Sonic (Nintendo as well)
Sonic RPG (the reception of this game in Japan is iffy, because of Bioware doing the development)
Sonic Rush Adventure
Big games for Wii at TGS:
-Nintendo:
Disaster: DoC (not sure if it will be shown or not)
Kirby Wii
Mario & Sonic again
Mario Kart Wii (again, this will be huge)
Super Mario Galaxy
Super Smash Bros. Brawl
Wii Fit (going to be HUGE in Japan)
Wii Music
-Square Enix:
FFCC:CB
Chocobo's Dungeon Wii
-Konami:
They still have an unnamed Wii RPG, so hopefully we'll get info on that. Otherwise not much.
-Capcom:
RE:UC
Devil Kings 2 (Sengoku Basara 2 in Japan)
Zack and Wiki
-Sega:
Alien Syndrome
Ghost Squad
Mario & Sonic (also counts for Nintendo)
NiGHTS
That's all I can come up with. KH will be anounced, but we don't know what console that will be on yet. It does seem like there is a good chance it could make the Wii, but better not to assume.