For me, there was a top 5 of Alonso, Hamilton, Vettel, Raikkonen and Hulkenberg then a gaping chasm to the rest, who have all had seriously disappointing moments in the season (perhaps excluding the Toro Rosso and "new" team drivers, who are difficult to judge).
In the rest of the team principle's top 10 we have Button (who went missing for the first half of the year), Webber (who had a disappointing second half of the year), Rosberg (who I would say was outperformed by Schumacher overall), Perez (who lost the plot once he knew he was going to McLaren) and Massa (really...). My 6th-10th would probably be Maldonado, Perez, Schumacher, Webber and Button but I honestly can't fill those positions in any way that seems satisfying because they've all been especially crap at various points.