Our gaming group tends to binge on a given game; if we like it, we'll play it dozens of times and then burnout and never play it again. One game that's stood the test of time is PowerGrid. It's rarely anyone's first choice, but it's the second choice for a lot of us, so it comes out often.
Often, at the end of the evening when we're pretty tired, we'll play cards, usually Mu. Mu is an amazingly deep trick taking game that has the advantage of working really well for 5 or 6 players. Also, it's a partnered game, but your partner is not fixed throughout the course of the game, which gives it an advantage over spades/bridge (which can be a drag if you have a weak partner.) It also has some delicious elements of backstabbing and subterfuge. I highly recommend it if you like games like spades/hearts/bridge.
If you have a regular gaming group, interesting meta-gaming manifests itself. For example, we have one person who's known as the "crazy guy", who'll do something random and destructive just for fun. Or certain vendettas will arise, and someone will sacrifice themselves in order to sabotage someone else. You have accept that sometimes folks will be irrational and be aware of meta-game in order to do well in the long run...