Indie Co-Op GOTY
Winner: Dungeon of the Endless (PC)
Dungeon of the Endless snuck up on most of the staff. A late discovery in the year after a long "battle" in Early Access on Steam, Dungeon of the Endless was a game developed by the community in so many ways. The four player co-op game feels like a social board games experience, friends team up through this rogue like that carefully combines several genres and gameplay styles.
While the game is incredibly deep, it's also accessible. It's challenging, but rewarding. It's retro, but new. Dungeon of the Endless is a complete package and represents what makes indie games so great, the risk of trying something completely outside the norm. Co-Op is a must in this to succeed, and when you do, the feeling is exhilarating.
Runner Up: Divinity Original Sin (PC)
Divinity: Original Sin evokes the same feeling of the classic isometric, squad-based RPGs of a decade ago, but with some new era touches. While co-op was supported in some of these older games (such as Neverwinter Nights), it was missing from many others. Divinity: Original Sin revitalizes the genre with modern day graphics as well as an emphasis on the co-op experience. This is done with little touches such as spell/skill combos between characters and dialogue interactions/voting between player characters that change story outcomes.
Each of the two players gets one protagonist which they can fully customize from the start. Other members will join the party at certain story points which can then also be distributed between players and fully controlled. The difficulty of the game's combat sequences combined with the immersive world (complete with a myriad of story-based and dialogue-driven quests) ensure that the players will communicate and strategize with each other at all times. Divinity: Original Sin is truly a game that does the concept of "co-op RPG" (with emphasis on "Role-Playing") right - an extremely difficulty task that few games can boast.