Are you into puzzle games at all? If you are, then a stab at the Professor Layton series of games is a seriously sound investment. I love them all.

And again, I cannot stress that Phoenix Wright is a stellar game series. I've not even played any of them yet (but I want to so badly!).

I'd definitely consider looking to see if you have a game or two that checks the 'group eligible' criteria. Multi-player games like CoD fulfil this, but Mario Kart is always a great party/friends game. Definitely have at least a game or two that you can play with friends that isn't online multiplayer.