Microsoft has announced that a new version of Geometry Wars is coming to Xbox Live Arcade next month from Activision.
Galaga Legions will also be coming, touted as the first true sequel to the original title. The same team who brought us Pac-Man Championship Edition are doing the honors, and it will be available next month.
Portal: Still Alive will come to XBLA this Fall with new achievements and levels.
And in 2009: South Park. Though details are few.
MS promises that XBLA will get a lot bigger this fall, and this is their strongest lineup ever, with over a million downloads.