Hamilton because of his instinctive, none text book driving.
There are many creative incidents that happened over his career that really makes him stand out from the rest.
Spa 2008 with Kimi, the weaving incident with petrov etc.
How he used the KERS strategically in 2009 when we were all introduced to the system. Most drivers weren't using it the way he was manipulating it.
His overtaking craft is also the most creative on the track. So much so that other drivers have implemented some of his moves the following years. He's a real edge of the seat overtaker too. DRS has taken the shine off of it of course, but he's still doing things where u must ask if the guy has lost his mind doing that in that corner.
Monaco, overtake on shumacher turn1 comes to mind. Also the double overtake on shumi and sutil in china as well. Overtake on button in china turn1. Oevrtake on Alonso Silverstone 2011? His overtake in germany on the outside of alonso to take the win. Just to name a few.
He's probably the fastest over a lap, and maybe if we had refueling still, over a race, but i think that is just one aspect of his abilities. His main signature is his driving style which contributes to his speed and creativity.
I think Alonso is the best driver, and yes he's my second favourite driver. It's contradictory, but these 2 drivers even when they were in the same team, i was a mclaren fan back then, so those 2 were my picks.
Alonso is not necessarily the fastest driver out there. But he has a "beast mode"
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which you don't really get with the other drivers. And if they have that mode, (Webber) they crash soon after that. He's able to maintain that for a race distance. That's where his in race speed comes from. He seems to have a never say never attitude. You see this when he loses the championship to vettel these couple times. You look in his face, and you know he's trying to turn back time, even when it's all said and done.
They say hamilton wears his heart on his sleeve, but i think Alonso is the most guilty party in that sense. The man is a maniac.
Not withstanding this best driver thing varies, it depends on who is paired with who. If Alonso is paired with Lewis, i wouldn't be able to say who's the best. I'll say Alonso now because of his experience and selfishness, which he can fully well exercise in ferrari.
As for Vettel, vettel is just vettel. I respect his achievements more and more each year and his dedication to work is note worthy, but he's boring. Much prefer Webber, though he lets me down 90% of the time. Vettel understands his machinery more than anyone else and he also understands the tyres more. You pick up a pattern that he does at the start of each race and at the end. You know he fully well understands when to push the tyres. He's a real student of the sport. But outside of that he's not really revolutionary or memorable. Can't deny that he's a championship winning machine however.