In F1 it's always the combination of driver and car.
Now there's a few things you need to do if you want to become WDC
1. get into a car that's capable of getting enough points to do so
2. (and just as important) beat you teammate
Vettel did both, three years in a row.
Out of 4 championship chances (2009-2012) he took 3. That's a good effort.
You can't really compare drivers in other cars, because we don't really know how to cars are relative to each other. If you want to know which driver is the best, you have to watch a spec series. In general I'd say in F1 it's about 80% car, 20% driver. Looking at RBR I'd say with Vettel it's something like that, but with Mark Webber it's something like 81% car, and 19% driver. Which explains the difference between them.
I'd say that Vettel, Alonso and Hamilton are the top three drivers, and roughly equal, but maybe with some different strenghts and weaknesses.
I think it's kinda funny that Vettels' drive in Brasil is seen as a brilliant drive by some, because he got himself in the last position through his own errors (bad start and collision). Usually he maximised the result with the RBR, just like Alonso does with the Ferrari, but not in Brasil. Because the maximum result there, would have been ahead of Alonso.
But he did a very good job in correcting his error, and did just enough to become WDC for the third time, so kudos to him.