One of the best features about the next title in the Mass Effect series is that you’ll be able to play co-op, as long as it doesn’t go full multiplayer in the form of deathmatch and other such modes, then I think it will stay unique.
Some co-op blurb:
Featuring four-player cooperative gameplay, multiplayer in Mass Effect 3 puts players in the role of a team of elite Special Forces soldiers sent to protect resources and assets that can help the war effort against the Reapers. Players will have the option of playing as one of six classes and from six different races: Human, Krogan, Asari, Drell, Salarian and Turian.
Multiplayer and other components of the Mass Effect 3: Galaxy at War system provide alternative ways for players to wage the final war against the Reapers. The new system will also connect players to their BioWare Social Network accounts to stay up to date on the latest Mass Effect 3 news and access downloadable content (DLC) and add-ons.