Like Jamie Whitham always said in SBK, about his mate Carl Fogarty, even if you have the best bike around, you still have to ride it. He may have been quoting Barry Sheene.
Or, Jeremy Burgess, Rossi's crew chief (and formerly Mick Doohan's) has the 80/20 theory where it's 80% rider, 20% bike. In cars it's 80% the car, 20% the driver.
You can see Rossi's talent by comparing him to Colin Edwards. Edwards is no slouch, being a World Superbike champion and Suzuka 8-hour winner (With Rossi on a shared Honda) and when he's fast, Assen or Seca, he's up there, but the rest of the year, his talent isn't enough to let him keep up with Rossi.
Now, F1 comes down to pit changes and team orders. There's no actual action on track any more.
So, to precis, I find it very difficult to find a car-racing sport that interests me these days. I hate "who has the best car" sports. Maybe A1GP should be the one.