Both Gaming Bits and Xboxic have posted a list of most of the known upcoming games. All of the titles have been announced in one place or another before (the latest list coming from the September OXM), and it's missing a couple of minor or untitled games ( Butterfly Garden, the next NinjaBee game codenamed SWAT, and Jeff Minter's upcoming title ), it's still a good list.

For those too lazy to click a link, here's the list (with the additions):

Alien Hominid
Assault Heroes
Butterfly Garden
Castle Crashers
Chess
Contra
Cyberball
Defender
Dig Dug
Diner Dash
Heavy Weapon
HoopWorld
Jeff Minter's upcoming title
Lumines Live!
Mad Tracks
Mega Force
Mini Golf
Ms. Pac-Man
Mutant Storm Empire
Novadrome
Paperboy
Pinball FX
Rally-X
RoboBlitz
Root Beer Tapper
Scramble
Small Arms
Sonic the Hedgehog: High Speed
Super Contra
SWAT (Codename for NinjaBee's next project)
Texas Hold 'Em
Time Pilot
Totem Ball
Track & Field
Ultimate Mortal Kombat 3

UPDATE: How could I forget Chess (announced as part of the IGN interview with Greg Canessa) :(