Kotaku- "Batman: Arkham City is a wonderful and violent video game. It's rated T by the Entertainment Software Ratings Board, the group that applies ratings to all major games released in the United States. T games are for gamers who are 13 or older.
Halo: Combat Evolved Anniversary is a remake of a beloved sci-fi first-person shooter. It was rated M, for audiences 17 and up.
Both games came out last fall.
The funny thing is that, after playing both games, I would have told you that Batman deserved the M and that Halo, a tame shooter by 2011 standards, would be a T.
How did these games get these ratings and what's the difference between Batman's T and Halo's M? First, let's look at the games, then I'll tell you what the ESRB said."