try "Betrayal at House on the Hill" in your group if you haven't already. It's a blast and has several (~60) different scenarios where one or more people betray the others midway through the game. each game is super dynamic and a new house is built each time.
Other games i play/have:
7 Wonders - great 2-7 player where you compete to build a city with cards and tokens, and gets better with more people.
Yggdrasil - Pretty strategic co-op game where you are fighting Nordic demons and gods. 2-6p.
Forbidden Island/Desert - two other co-op games, easy to pick up and play. 2-4p
Catan - resource based Like monopoly. not my style of game. kind of a stupid luck dice roll game anyway.
Pandemic - Looks cool. Co-op game fighting four different diseases 2-5p?
Munchkin - fun card game where you can team up and/or betray people. 2-6p
Exploding Kittens - eh, it's ok. reminds me more of UNO.