Agricola works fine with 2, but it is not the place to jump in if you are looking for something accessible for a casual wife. Get her hooked on games first
Catan Card Game is still my wife and my favorite 2 player game. If you guys like it, you can grab an expansion pack (with 6 expansions in it!), for one of the best deals in gaming too, as each of those expansion sets are awesome.
Dominion is casual, and works out pretty well 2 player, though I like it better at 3-4.
I'm not as much of a fan of Lost Cities, but both Ingenious and Great Wall of China (same designer) are pretty awesome. GWoC supports more than 2 as well, though I've only ever played it one on one.
I'm on a huge Race for the Galaxy kick lately, and the wife and I have played it 2P quite a bit, but I'm not sure if I can recommend it mainly as a 2P game, especially if you're looking for something a bit more casual. It's got a bit of a learning curve.