Clue and Life! It's not a board game but we were introduced to a game called Rummikub by the lady that ran the bnb we got married at, and it is very fun too!
When I was young, all we had was board games. We played Monopoly, Life, Yahtzee, Scrabble, and Chinese Checkers. Later, I got into chess, and loved that, but haven't played in years because I don't have someone to play against.
Risk when I was young... then each member of my family graduated to "bookshelf games" like Twixt, Ploy, and Feudal. We modified the rules in Ploy and Feudal, made the games better and faster. Some of my seven brothers were into complex war games, the kind with heaps of counters and plenty of logistical considerations... they'd literally play a game off & on for a month! Nobody has time for that sort of game anymore, youngsters nowadays are into flashy video games where little imagination is required, pffffft. I still have Twixt, Ploy & Feudal on a shelf in my home, maybe one day when I'm older I will find another worthy opponent to play these excellent games. Back in the day, friends & I had so much fun playing them... we'd even party and drink beer while playing games, other friends watching if they didn't actively participate. Just the way things were done in those days, it was a separate reality...
I have never played Monopoly, but I do love certain board games.
Every Thankstaking (what we do for Thanksgiving), Yule, and Twelfth Night, we play a board game with our adult children, my husband's sister, our son's best friend, and whoever else is invited that year. We also play at my mother-in-law's house on Thanksgiving and Christmas. Our favorite board game for larger groups is The Betrayal at the House on the Hill played with teams; however, our favorite game to play with large groups is Gloom, which is a hilarious, slightly morbid, card game. We have the basic deck with two expansion decks onhand when we need them.
For smaller groups, specifically my husband, children, and son's fiancee (and sometimes my son's best friend), we play Clue, Betrayal at the House on the Hill, and Forbidden Island. The strange thing about when we play Clue is that more than half the time we play, my character is always the murderer. We do not have any set days that we play the games, though. It is just whenever.
My husband and I do have a favorite to play on our own: The War of the Ring. It is a bit like Risk but is influenced by Lord of the Rings. We absolutely love it! He and I also play chess.