We're a family of boardgamers, our collection is getting quite impressive... they provide a great way to socialize and to disconnect for a few hours. They are great for kids, and adults.
We love cooperative games the most, the onese where all the players are trying to defeat the game itself. The cool thing is that they can also be played solitaire and a player can control multiple characters.
Some examples are Pandemic (you should definitely try it, best game design ever), Dead of Winter (where one of the players could be a traitor), Ghost Stories (almost impossible to win!), and Arkham Horror (our favorite, based on HP Lovecraft's writings... but it takes about 6 to 8 hours to complete a game...).
A great non-coop game to try is: Ticket to Ride.
The only game I am afraid to try is Diplomacy... apparently you're going to lose many friends in real life because of that game.
Just to give you an idea of what Arkham Horror entails...