My recommendations:
Budget games (in some regions):
Uncharted: Drake's Fortune (demo available)
Ratchet & Clank Future: Tools of Destruction (demo available)
Resistance: Fall of Man (demo available, beginning, later parts become better)
Motorstorm (demo available)
Ninja Gaiden Sigma (demo available)
PSN
Super Stardust HD (demo available)
Warhawk + packs (demo available)
Super Ruba Dub (demo available)
WipeOut HD
PS3 full price:
Resistance 2
Motorstorm 2 (IMO sucky demo available)
Metal Gear Solid 4 (demo available)
LittleBigPlanet
Grand Theft Auto 4
Plenty of other worthy titles available which I haven't played enough or are good if you like the genre. For example Heavenly Sword (multiple demos available), Folklore (multiple demos available), Hot shots Golf (multiple demos available), Assassin's Creed, Call of Duty 4 and 5, Bioshock (demo available), BurnOut Paradise (demo available), etc.