Close call for me between the Enzo and the Zonda F. In the end, I went with the Enzo. IMO, it just has that complete supercar appeal. The looks, the doors, techno-wizardry dialed to 12. It's not classically beautiful, but then few cars in this group are; it's still very stunning in real life.
As for what other cars should have made the cut, I'd love to see how the McLaren F1 and Veyron would do at the Nurburgring.