I suppose that the other options would be Mancebo, Sastre, Menchov, Simoni...
Feel free to add in anyone I've missed to the discussion.
I have voted for Basso. The post Lance years are a tough call, but I lean towards Ullrich in '06 (he had great form in the Tour De Swiss lead up, there was a lot of ITT, a couple of the MTF's were not that hard, and we know how strong T-Mobile were), partly on the theory that even Robo would have been a little exhausted backing up from that Giro. In '07 Jan is another year older and possibly a little fatter again after being too satisfied with his second Tour title! Although then again, I believe that Rasmussen should have won the actual '07 race that took place. But would Michael have been afforded such freedom on that early mountain stage by super strong CSC and T-Mobile squads?
I know that the time produced by AC and MR on PDB is very impressive, but I just find it hard to see a Basso in peak form being worse. Would most agree that Basso's climbing in '06 defeats the exploits of the other two?