Pandemic (on any higher level than easy) is so hard to beat... I played it with my friends (also boardgame geeks like me :P) and manage to win 2 maybe 3 of 10 games. Still it's sooo great and is one of my favs.

I can recommend all of you a polish game Queue made by Polish Institute of National Remembrance. I know that it has been translated to English, German, Spanish, Russian and Japaneese and heard that it can be bought outside Poland (or shipped abroad).
More info: http://ipn.gov.pl/en/news/2011/the-queue-board-game
http://www.boardgamegeek.com/boardgame/85325/kolejka

Or Warsaw... I know dozens of board gamers here :)

Maaan, nice list over there. Over 60 games in collection... Wow, I'm jealous ^^
Bang! is really nice. Great socializer for a party. I recommend buying at least 2 sets and playing with more than 10 players. It's wild wild west everywhere!