The Neccesity Games

I wondering what you guys think are the neccisity games for the three current generation consoles (and potentially others). By which I mean if you get an Xbox 360, or a friend is getting one, what game(s) is it you absolutely must get?

I know if I was to get a PS3 I would absolutely need Heavenly Sword to show off my graphics and probably MGS4.

What about you guys?

For 360: Gears of War, Halo 3.
For PS3: MGS4, LBP.
For Wii: SSBB, Super Mario Galaxy.
For PC: Crysis, STALKER, TESIV, The Orange Box.
For Multiplat: CoD4, BioShock, GTAIV.