Stoner doesn't sell anywhere near as many bikes as Rossi and other top riders in the sport do/have.
Even Lorenzo is much better known to mainstream fans. Stoner's a very good rider, but he has no personality, isn't very marketable and is always putting his foot in his mouth. It's why Ducati were happy to pay Lorenzo more - just as much talent and far more marketability.
Well from a marketing/money making point of view, you may be correct here. Lorenzo is determined, talented and he does the after race theatrics which some people love, but lets take it a step further.
Say you're a rider looking for a ride in the smaller gp classes, then the bigger classes. Some are fast, some are from the right country, some are marketable or bring sponsorship money, some are a combination of all three.
if you have all 3, for sure, then you get gifted the best rides in the best factory teams.
If you have 2 out of 3. It depends. Nicky hayden only won a world championship for honda, but dani was from the right country and was the sponsors pet boy, so that trumped hayden in terms of who was no.1, who they developed the bike for.
What if you're just fast? are you going to get a ride? maybe, maybe not. If so, it'll be with a satellite team with left over factory bits, so you better be extra fast to compensate.
If you're from the right country, have sponsorship money, but maybe aren't as fast, are you going to get a ride? maybe, maybe not. Is that good for marketing? maybe. Good for the sport? No.
Barry sheene was from the wrong country (not spanish or italian), but he was smart, so he invented the marketability. and it helped that he was fast.
But Doohan, rainey, roberts, schwantz, lawson, gardner, mccoy, would we have seen all these guys come through in the current environment, because they're weren't marketable in the sense of rossi or lorenzo, they weren't from the right country or have rich sponsors, lucky for us they were just fast enough to get noticed. Unfortunately i'm wondering whether that's enough nowdays.