Last years Tour I would put Contador and Schleck as the two best (probably on the same level), Samuel Sanchez behind that, and Menchov after that.
I would love to see Rujano find his 2005 legs again, but I just don't think it's very likely. Over the last five years, Menchovs climbing palmares is clearly superior to Rujanos.
Rodriguez is a wild card. He seems to have a great shape maybe a bit too early, but he should still be fresh because he hasn't shown much before this week. The part of the Cauberg where he attacked is about 12% btw. But the Zoncolan, Grossglockner and Finestre should suit him very well.
If everyone arrives in shape, this could be one of the most hotly contested Giro's in ages, I really can't wait. The only potential to spoil the party is a too dominant Contador.