I don't even understand your crazy American ratings... in New Zealand I'm fairly sure it goes:
G - General (kid's games)
PG - Parental Guidance advised (like Ratchet & Clank)
M - Mature audiences (eg. inFamous, not for kiddies)
R13 - Restricted to 13 years (on second thought, this one might just be for movies)
R16 - Restricted to 16 years (blood, swearing, war scenes etc.)
R18 - Restricted to 18 years (basically any game that contains sadistic elements or excessive gore)
Australia has (for games):
http://www.classification.gov.au/
G: General (Nothing)
PG: Parental Guidance Advised (Lasers, robots, one or two mild curses) [Motorstorm, Ratchet & Clank, Warcraft III]
M: Mature (Bullets, partial nudity, swearing, deaths) [Burnout, Mirror's Edge, Starcraft]
MA: Restricted to 15+ (More partial nudity, blood+gore, torture, swearing) [Pretty much everything else. L4D, TF2, HL2, COD, Halo, Doom, Resistance, Killzone, Uncharted, Bulletstorm, Company of Heroes, GTA]
Our movies also have R18+ (Nudity, gore, gore, violence, death, dismemberment, cluster-f-bombs). [Quentin Tarantino, Dawn of the Dead, Taxi Driver, Se7en]
For us, Brink will probably be an MA15+, while as a movie it would be PG. If you hadn't guessed, I hate the OFLC. And we have no R18 rating for games, so they either get censored (L4D2) or just slapped with a 15+.