I went into some detail that's been covered here plenty of time because I'm considering posting this on another forum but I thought I'd post it here first and if there's any mistakes the knowledgable guys here could correct them for me. It should make for some interesting discussion anyway. I was going to just post the numbers and let the discussion go from there but I got a bit into it and stared trying to analyse things myself. If you don't want to read all the info just skim the stats because I do believe they tell a very interesting story.
I've had a lot of time on my hands lately due to some circumstances out of my control so I've taken some time to try at my amateur level taking a deeper look into Rossis record and how much tyres may have played a part in his success. I know there is more knowledgable people out there that can shed a light on things I've either glossed over, got wrong or didn't know about but I think this is a good start at taking a real look at Rossi and trying to put his results into context. Rather than get into by cc limits and rules I decided to look at it from what happened with tyres and define the time periods by tyres.
2000 - 2005 Michelin SNS era
97 starts 53 wins
winning percentage 54.6%
5 titles
For those that don't know Michelin before they became the control tyre used an unfair tier system to decide who got their best tyres, which were reserved for the factory teams with development driven by one or two leading riders which gave those leading riders a big advantage over the field. It gave select rider/s a say in tyre contraction and could/would give them an advantage if they preferred tyres others that were quick did not. Rossi was that man during the era he competed in, as Doohan was during his championship years. Michelin techs during this time would get the data from Rossis(and before him Doohans) team on Saturday afternoon and make tyres to suit the rider and conditions perfectly for be race day on Sunday that night. The tyres would then be driven overnight to the tracks in Europe however logistics meant they couldn't be delivered for the fly always. For satellite riders as is spoken about in Stoners book, they got left overs which were sometimes mismatched making it almost impossible to be competitive against the factory guys on their special overnight tyres. Perhaps the best example of the situation and how important it was to be at the top of the tier system is Tony Elias win at Portugal in 2006. Pedrosa rejected the top tier race tyres that were bought in for Portugal because he felt they were too hard(for those that don't know Rossi prefers his tyres harder than most) Elias was next in line for the tyres and used those to take the win ahead of Rossi. The irony here is that if not for Elias getting Pedrosas discarded tyres, Rossi would've won the race, bagging an extra 5 points and won the title on race wins. Pedrosa who rode on the none tier one tyres crashed 4 laps in famously taking out Nicky Hayden the championship leader.
I think for this era/part of Rossis it's very important to draw a comparison to another rider who dominated during a similar era in similar conditions for better context. So a man who was in charge of his teams bike development and michelins go to guy for tyre development.
The best comparison I can draw is Mick Doohan who also won 5 straight titles in similar circumstances. They both even had the same crew chief which is perfect for making this comparison.
Rossi Doohan
81 starts 71 starts
51 wins 45 wins
63.0% 63.4%
5 titles 5 titles
It's evenly matched with Doohan having a slightly better winning percentage. Rossi certainly isn't head and shoulders above Doohan like the rhetoric that's pushed by certain sections of media and fans would lead us to believe. I think it's worth mentioning that Doohans entire career was on the 500s which were far more prone to both mechanical failures and spitting you off due to a much smaller margin of error. It does make Doohans run more impressive in my opinion especially when you account for Doohans almost career ending injury from which he never fully recovered. But from these stats we can say that without a shadow of a doubt that at worst Doohan was Rossis equal during their strongest years but he falls short on longevity and titles due to his horrific injuries. Without a doubt he would've won in 1992 if not for the injury but there is no proof in 93 and 99 he could've dominated as he did in '92 and '94-'98. Mocks dominance over Rainey and Schwantz in '92 is more impressive than anyone Rossi dominated during '01-'05 and I do doubt that Mick had a similar tyre advantage to Rossi would later have during the following years.
During those years Max Biaggi was Rossis strongest and most consistent competition but I would to point out, what's good for the goose is good for the gander that Biaggi was 30 when Rossi won his second title, the same age Rossi was when he won his closest title and was according to his fans old and past his prime. Gibernau was was 31 when he managed to get onto a bike good enough to challenge Rossi, the same age that Rossi was 'past it' according to some of his fans. While I don't believe that a rider in his early to mid 30s is past his best Rossi fans have consistently used this argument as to why he hasn't won a title in 8 years. You can not make the age argument for Rossi but then conveniently forget that his toughest competition during this time was in the same age bracket as Rossi was when he stopped winning championships.
2006 - 2007 Michelin era after abolition of SNS tyres
35 starts 9 wins 25.7% 0 titles
As you can see from these stats alone, immediately once Rossi lost part of his tyre advantage(though it must be pointed out he was still the leading man for tyre development) his results dramatically dropped. His winning percentage was under half of what it was in the years leading up while the 'Saturday Night Specials' were allowed to be flown in by DORNA for the race on Sunday. He failed to win both titles when he competed on a more even playing field. He seemingly choked in Valencia 2006 and was totally dominated by Casey Stoner on the Ducati in 2007. During this time Rossi fans and by extension Rossi for not condemning them belittled Hayden's title, calling it lucky. The next year once Stoner showed just how brilliant he was, the same fans vilified Stoner for winning and then made an attempt to belittle his title by giving credit almost solely to the bike and tyres. A theory that was later disproved by Rossis nothing short of epic failure in 2011-2012. Stoners championship win on the Ducati does remain the most impressive championship win during the MotoGP era.
2008 Bridgestone
18 starts 9 wins 50% 1 title
This was a strange situation to say the least. Rossi wanted Bridgestones, Bridgestone didn't want to supply Rossi and were happy to continue their work with Ducati, Suzuki and Kawasaki. Rossi threatened to retire if he didn't get Bridgestones, DORNA made sure that Rossi got Bridgestones. The factory Yamaha team must've already had a contract with Michelin because Lorenzo had to continue the Yamaha/Michelin partnership. Logically one could assume this starts to give some issues to Lorenzos bike due to the lead rider developing a bike for Brisgestones which were much different to the Michelin. This also took development away from Stoner and Ducati, Stoner requested DORNA and Bridgestone for the previous years tyre which suited his Ducati much better(according to the man that was riding the bike) as development started to favour Rossi and Yamaha as the previous Michelin development had. The request was rejected in an unprecedented move during a tyre war. Bridgestone went from not wanting to supply Rossi to favouring Rossis development in the blink of eye, it's reasonable to draw a conclusion that this was at the behest of DORNA who wanted their most marketable rider to win after Stoner, a more talented but unpopular rider hurt the bottom line with his dominant win in 2007. Rossi went on to win his last dominant championship, while Ducati and Stoner faltered trying to get the new design of tyres to work with their bike. Suzuki and Kawasaki's competitiveness drastically dropped once Bridgestone started working with Rossi and Yamaha which is I think more proof that Bridgestone like Michelin before them favoured Rossi, which once again have him a tyre advantage over the field.
The issue is for me is not that Rossi was able to switch brands it's that he was the only rider able to switch as others had asked. It's also an issue for me that after years of working with Bridgestone to get their tyres competitive Ducati were bent over and ass ...... by DORNA by having tyres that suited their odd bike taken away from them. Stoner famously commented about Rossis attitude by saying he shouldn't complain about tyres after so many years of having a tyre advantage over the field
2009 - 2016 control tyre era
138 starts 17 wins 12.3% 1 title
2009 - 2016 without Ducati years
103 starts 17 wins 16.5% 1 title
The control era begins with Rossi winning by his tightest ever margin. While great riders like Stoner, Lorenzo, Pedrosa and Marquez coming through to the premier class just before and during this time is certainly a factor in his declining results the effect of no longer having specially tailored tyres can not and should not be discounted. Perhaps the biggest irony about the control tyre era that was by all accounts set in motion by Rossis demand to switch to Bridgestone is that it's because of the control tyre and Bridgestones development being taken away from Ducati the bike become almost impossible to win on unless you had the godly talent of Stoner. Rossis demand is why he failed so famously when he jumped ship to Ducati after Yamaha dared give Lorenzo equal treatment.
Both Bridgestone and Michelin wanted to keep the tyre war going and did not want to switch to a control tyre. Knowing they couldn't build a Honda or Yamaha better than Honda or Yamaha, Ducati requested to start from scratch with Michelin but were denied by DORNA. The control tyre saw Ducati decrease in competitiveness, Suzuki take an hiatus and Kawasaki dropping out of competition completely. The rhetoric pushed by DORNA and co was that it would increase competitiveness for satellite riders but from 2009-2015 only Stoner, Marquez, Lorenzo, Rossi and Pedrosa won multiple races while Spies was the only man outside of the 'aliens' to take a win but it was on board a factory Yamaha. Ducati would go winless from 2011-2015.
During his time at Ducati contrary to what some may try to say, Ducati have Rossi everything he asked for. Nothing proves this out more than the switch from a trellis frame, one of the most iconic parts of Ducatis DNA to a twin bar aluminium frame. The issue was likely trying to fix too many problems at once rather than methodically going through the bike to fix one problem at a time and staying for the long haul. Rossi took a bike that Stoner used to win 3 of the last 6 races in 2010 and was winless in 2011 on the same bike. Upon his departure in 2012, Ducati was probably in worse shape than before and commonly finished behind the satellite Hondas/Yamahas but in front of the CRT machines.
Rossi doesn't stack up well against other great riders that he has competed against. While fans will point to his age there is very little if any evidence that age without injuries will effect performance riding a motorcycle. The age range of 25-35 will show very little to no drop off for reaction time/reflexes. There's the argument used about athletes from other sports being on a downward slide in their mid 30s but the key difference here is that it's the wear and tear on their body taking its toll. Their minds still react and see the same things but their body let's them down. With modern training and nutrition sports that are just as reaction based but harder on the body such as MMA or Boxing are seeing athletes retain their championships well into their mid to late 30s. The age excuse for this reason is I believe null and void.
Rossi is certainly one of the greatest riders to ever race but he in my opinion isn't the clear cut GOAT. His losing record against all but one great rider, who isn't at the level of Marquez, Stoner and Lorenzo has to hurt him when speaking of all time standings. His fans fall back to the 9x world champion as the reason why he is unequivocally the GOAT but there's riders with more championships, Agostini having won more than anyone else. While his longevity has been nothing short of amazing his results don't stack up once strong competition started coming to the premier class.
Rossi vs Stoner 2007 - 2012
102 starts 99starts
21 wins 38 wins
20.5% 38.4%
2 titles 2 titles
Rossi vs Pedrosa
191 starts 182 starts
35 wins 29 wins
18.3% 15.9%
2 titles 0 titles
Rossi vs Lorenzo
Overall
2008 - 2016
156 starts 156 starts
26 wins 44 wins
16.7% 28.2%
2 titles 3 titles
On the same equipment
2009-2010 2013-2016
103 starts 106 starts
17 wins 34 wins
16.5% 32%
1 title 2 titles
Rossi vs Marquez
72 starts 72 starts
9 wins 29 wins
12.5% 40.3%
0 titles 3 titles