Of games that have been released so far this gen these are probably the ones that are worth purchasing:
PS3
Grand Theft Auto IV (PS3 higher rated version but new dlc coming soon only to the 360 version.)
Metal Gear Solid 4
Valkyrie Chronicles
Little Big Planet
Uncharted
Ratchet and Clank Future
Resistance I & II
Heavenly Sword
Folklore
Prince of Persia
Warhawk
GT5 Prologue
Ninja Gaiden Sigma
Devil May Cry 4
Grid
Unreal Tournament 3
Mirror's Edge
Pixel Junk Eden
Pixel Junk Monsters
Calling All Cars
Wii
Mario Galaxy
Zelda: Twilight Princess
Super Smash Brothers
Metroid Prime 3
The World of Goo
Mario Kart Wii
Lost Winds
I know that with all I have for PS3 and 360 here people will say, "Oh, you're slighting the Wii!" But, I'm really not. There are a ton of classic games that you can purchase from Nintendo Channel's and download for the Wii, and if you would like to see them go look for them at http://wii.ign.com.
360
Bioshock
The Orange Box
Halo 3
Gears of War I & II
Fable II
Call of Duty 4
Mass Effect
Oblivion
Fallout 3
Lost Odyssey
Braid
Pacman Championship Edition
Geometry Wars
Dead Rising
Lost Planet
Tomb Raider Underworld
Golden Axe: Beast Rider
Assassin's Creed
Tales of Vesperia
Ninja Gaiden II
Sonic Unleashed
The Crackdown
Dark Sector
Skate
Kameo: Elements of Power
Banjo Nuts and Bolts
Viva Pinata 1 & 2
Some more Arcade games I haven't listed.
With all of these it must be a better gen than some folks think.
Heavens to Murgatoids.