OK, time to get this started for the classic discussions forum. Let's start building a list that others can use as a guide - even if your suggestions don't make the list, at least your suggestions get seen! These threads should be especially handy to people who got their systems recently and want to start out with the "A List" of games to pick from.
So let's start the "A List". What would you add to it?
NOTE: * = exclusive to this system (for now)
Beautiful Katamari *
BioShock
Call of Duty 4
Crackdown *
Dead Rising *
Dead Space *
Earth Defense Force 2017 *
Eternal Sonata
Fable 2 *
Fallout 3
Gears of War
Grand Theft Auto IV
Guitar Hero (series)
Halo 3 *
Left 4 Dead *
Lost Planet
Mass Effect *
Mirror's Edge
Oblivion: Elder Scrolls IV
Orange Box
Resident Evil 5
Rock Band (series)
Saint's Row *