Not sure I can add much to what Ruslan says, but I'll throw my two pennies worth in nontheless...
Certainly.
he was the best driver on the grid
Impossible to say.
Now you can stop reading there, or read my waffle below
The combination of chassis, engine and driver were certainly the best package, of that there is little doubt. I don't have an opinion on who was 'the best' in 2010, or any of Vettel's championship years for that matter. At the time he was indeed in many/most peoples top 3, but few (and I mean of those travelling with the circus, career pundits etc) would go so far as place him above
the other two and more recently, 'those in the know' you'll find have been re-visiting those years of domination with new questions emerging. For what it's worth, I do not particularly rate Webber as an F1 driver. This is no criticism of Webber per se, he's a bludee gud bloke ya-know?, but it is a reflection of my view of using him as any kind of yardstick for team mate comparison.
Finally, when i cast my mind back to that time, I'm reminded of Kubica at the top of his game in a relative shit-box, Rosberg utterly dominating the Michael, Alonso challenging Vettel almost throughout when the car had no right to do so and Button and Hamilton pushing each other (with a large part of either drivers failure to truly challenge for the title probably being because of McLarens lovely, but slightly flawed equal treatment policy, even during those inter-team battle years). You could make a pretty good case for any of the above if you wanted to isolate one as the best, but it is impossible to truly isolate driver performance in a team sport. Yes you can pick out faults for all above, but the Vettel of the past two seasons is forcing difficult questions to be raised, even amongst his biggest fans.
Back to 2021, i think we'll have to wait and see. If he is consistently behind Leclerc by mid-season, i could well imagine a vacant seat at Ferrari.