Very close between Vettel and Alonso, Vettel's ability to pull something out the hat when he needs it most gives him the edge, just.
Kimi and Lewis next up, but under the right conditions just as good as top two. I think we will find out a lot about Hamilton this year as i think he needs to give Rosberg a good beating, Rosberg is fast but not top class.
Button and Webber next up and a bunch of drivers who could be brilliant but have to prove it such as Hulkenberg
This is close to how I see it, with Massa also in the Button and Webber class (now that he has gained back some form). It is not a top three or four any more, but a top two. Alonso is the fixed reference. We have seen him under so many different situations that his stock is unlikely to go up or down much. The same could now be said for Kimi. Vettel and Hamilton could yet go up or down a level, depending on how much of their apparent potential is really there.