I just finished the first season of Ultimate Survivor Kaiji. Damn good and intense. Somebody else should watch it so I have somebody to talk to about it.
Haven't watched it yet but the manga itself is already damn intense! The author really know how to build up tension and push it to the limit before he allow the protagonist to taste the wonderful victory. I remembered reading the final chapter of the second arc ( the pachinko arc, I think) while listening to the final boss theme of Touhou Ten Desire. Man, that was something.
Ooh, man, it's true. Especially when I was watching the E-Card story, I couldn't believe I was so intensely focused on two people playing a card game. But... it makes sense, really. The rules for the game were incredibly simple, but that was meant to put more focus on the psychological aspect, and Kaiji's all about head games.