I've played board games more than I care to remember and the people I played with were "expert-level" board gamers. This made a game like Arkham/Eldritch Horror un-enjoyable. Took entirely too long to setup and too long to read through all the erratas through the play-through. You'd have the "experts" jumping back and forth between the same locations over and over again knowing the odds of favorable outcomes and correcting casuals who just wanted to play the game but continued to lose sanity in the witch house or some other place they had no business being in.
We basically broke Dracula. Virtually impossible for Dracula to win with competent hunters. Had to house-rule Marvel Heroes to make it enjoyable.
Given that our gaming group started to have more wives/gfs we started to move away from games like Arkham to games that casuals could participate in and yet "experts" could still enjoy. This is reflected in my list below. A good game should be able to merge casuals with experts and create a unique gaming experience each time.
Favorites:
Citadels (Love this game but entirely depends on your group)
Through the Ages
Agricola
Galaxy Trucker
Puerto Rico
Cosmic Encounter (Yes. I know this errated all to hell and can be complex but it's my favorite game and I can't help but mention it. Plus, no one but me loves this game in our group)
Bohnanza (super casual, easy)
RA (friends enjoyed it, me less so)
Recently we've been playing some game where you draw two decks, meld them and play. Forget the name.
Also substitute drunk expert for any place above where casual is referenced.