It's so funny how far down the rabbit hole goes. There are like tiers of board game snobbery. Got the traditional / family games (Monopoly, Risk, Password), then there are the new age entry level stuff (Settlers of Catan, Carcassonne, Dominion), and then there are games like Terra Mystica, Power Grid, Agricola, etc. that are for the "serious" board gamers. Seems every hobby has some sort of structure.
I mention this only to give the newcomers an idea of where to start, in case you're interested in dabbling. Settlers, Carcassonne, and Dominion are the best games to try out and get hooked on. If you like them, then you're screwed, because it can get dauntingly expensive (Dominion will result in several expansions bought, likely totaling well into the hundreds--FOR CARDS). For people who don't mind setting a few hours aside for one game that is gratifying (to win or lose--for me, anyway), then the latter set are good choices. My personal top 3:
1. Dominant Species (worker placement, LOTS of choices, called a "brain melter" due to the potential "analysis paralysis," most fulfilling experience).
2. Mage Knight (mentioned in previous post--LONG game, but oh-so gratifying).
3. Agricola (with so many sets of cards and variation in setup depending on how many people are playing, it's always a new experience).
There are tons of other great games. Lots of great "light" games, too. Carcassonne and Settlers of Catan online suckered me in. Met some great people through local meetups--worth checking your area through meetup.com if you don't have some friends to play with or who are interested.