My favourites:
*****: Froome
****: Quintana, Porte
***: Aru, Contador, Bardet
**: Fuglsang, Meintjes, Valverde, Chaves
*: Martin, Thomas, Majka, Yates, Uran
Froome hasn't been the dominant rider that we've been used to seeing, but I still see him as the main favourite. Quintana will be interesting to see, it may be a bit too high.
It will be interesting to see how Fuglsang and Aru will be working together. If they're both decent in the GC when the race goes to the Alps (or maybe even earlier) they will be a dangerous duo, just like we saw at Dauphine. I hope that Fuglsang is in at least the same shape as then, while it seems like Aru has stepped a bit up, dominating the national road race.
For the green jersey, I don't see anybody competing with Sagan (unless he has a major crash). The main contender should be Kittel, as there's a good amount of flat stages this year, but Matthews will also be interesting, as he is also able to take some points on the slightly tougher stages.
The entirely flat stages should be between Kittel, Greipel and Demare, though I don't want to count Cav too much out of it. Groenewegen, Kristoff and Bouhanni will also be very interesting.
Meanwhile the polka dot jersey will be hard to guess. I would say that Pinot and Rolland seems to be the best guesses. Pinot won't get much help in the mountains, which is why I don't have him in my list of favourites for the GC. Also he didn't look too strong in the ITT Nationals. Rolland finally seems to be going all in for the polka dots. Meanwhile a rider like Majka could quickly end up going for the dots instead of the GC. Other interesting riders could be Atapuma, Gesink, Bennett and Barguil.
The white jersey seems to be between Meintjes and Yates with Buchmann as a strong outsider.