For quickie fun card games to appeal to those who like '6 Nimmt', I suggest 'Bohnanza', 'Guillotine', 'Sticheln', and 'The Great Dalmuti'. Especially 'Sticheln'.
A great two player game is '7 Wonders: Duel', put out by the developers of 7 Wonders. Significant differences -- same theme, different game. I really miss playing this game with my now dead gaming buddy.
A wonderful game (not for real time) is the classic Avalon Hill game 'Civilization', or its child, 'Advanced Civilization'. Not sure how the trading phase would work though.
Other fun light board games:
Castles of Mad King Ludwig -- excellent for two as well as 3 or 4
Vikings
Cosmic Encounter (old)
Kremlin (old)
Modern Art (the original)
Illuminati
Alhambra (though I guess you had it and had to yank it)
Other fun more complex board games:
Agricola
Euphrat & Tigris
Container -- economic shipping game
P.S. I tried to nominate 'Sticheln' on the board game geek site you advocated, but I don't think I succeeded.