NO Multiplayer for Batman Arkham City
"There have been a number of rumours circulating about a multiplayer mode in Batman: Arkham City so let me start by saying, once and for all, that Batman: Arkham City is a 'single-player only' experience," a rocksteady dev told IGN. more articles here
Torchlight 2 CO-OP ACTION
The most exciting new feature of Torchlight II is the multiplayer element. Play with your friends, and use the free peer-to-peer matchmaking service to meet new players of a similar level and interest. Together players will discover expansive randomized outdoor areas and deep ominous caverns; random instanced and persistent dungeons, a huge variety of all new monsters and villains, endless variations of loot to find, and quests to complete. Players journey through the perilous Overworld, enjoying all new weather features, time of day events, and a rich and cunning story to drive gameplay. The digital download is to be expected in 2011.