I reckon it depends just as much who’s in the other cars.
Imagine if in this year’s championship, we’d seen the Vettel from 2009 and early 2010 – making mistakes, not so great in qualifying, crashing a little.
I think it’s fair to say that Button would have won the championship, beating the highly respected Webber and the ‘crash kid’ Vettel in a faster car.
What do we conclude? Button’s capable of winning the championship in an inferior car. Just not when the guy in the best car puts in a season like Vettel just has… a season which has to be one of the best performances in a dominant car ever.
The same goes for a lot of others. I bet Kubica thinks that in 2008, when there were no great driving performances (on the level of an Alonso, Schumacher, Vettel or Mansell), he could have won the championship in either the McLaren or the Ferrari. He came close enough in a Sauber!
So it’s a poor yard-stick. Winning a championship with an inferior car almost always requires your rivals to make mistakes. That means it depends on luck. Vettel might never do it, but that doesn’t make him a bad driver. And it doesn’t mean he can’t attain greatness in the years to come.