I might as well list some good PS3 exclusives. Somebody else do 360, I don't really know much about it, and I'd just end up using Metacritic or something.
MGS4 (and it's staying exclusive)
Uncharted
Killzone 2
LittleBigPlanet
Valkyria Chronicles
Ratchet and Clank Future: Tools of Destruction
Resistance 2
Resistance
Heavenly Sword
Folklore
Ninja Gaiden Sigma (lol, not really an exclusive, but it's only on the PS3 this gen)
Gran Turismo 5 Prologue
MLB 09
MLB 08 (Those two only in NA, though, I think)
MotorStorm
MotorStorm: Pacific Rift
Warhawk
Singstar
Metal Gear Online
Disgaea 3: Absence of Justice
The Eye of Judgement
PSN:
Flower
WipEout HD
Pixeljunk Monsters
Pixeljunk Eden
Super Stardust HD
Ratchet and Clank Future: Quest for Booty
flOw
Crash Commando
Comet Crash
PS1 Classics
The Last Guy
Savage Moon
Linger in Shadows
Tekken 5: Dark Resurrection
Hot Shots Golf
Echochrome
Siren: Blood Curse
(Near) Future:
God of War III
Uncharted 2
inFamous
MAG
Heavy Rain
GT5
FF Versus XIII
Ratchet and Clank Future: A Crack in Time
Quantum Theory
Under Siege
WarDevil
Resistance 3
Trine
Fat Princess
EDIT: Okay, I'll add more.
(Former) Lead Moderator and (Eternal) VGC Detective 
