The recent non-sense by Piquet jr (see the other thread) made me think of the drivers who seem to have a great impact on the sport and raised the game overall.
So here's my list:
I start from 70s, because it is hard for me to trace things much before.
1) Jackie Stewart
Was the fastest guy of his time and shown how being reserved and analytical at the wheel gives you results. Made people turn their attention to the safety. His winning record stood for very long time.
2) Niki Lauda
Not too sure about him, but it seems like his "presence" during late 70s and early 80s was very prominent. He also turned the focus on consistency.
3) Alain Prost
Wasn't named "professor" for nothing. Had speed and was very sensitive for his car. Payed a lot of attention to fitness. I heard that he was the one who introduced those fructose syrups that drivers sip all the time and was one of the first drivers with his own physio.
4) Ayrton Senna
You couldn't beat him with a talent alone. Apart from his legendary speed, he was the guy that checked all the boxes. If there was a slightest thing which could give him advantage, be it setup change, training, food or meditation he'd look into that.
5) Michael Schumacher
Set the new level of driver/team cooperation, new level of physical training, was probably the first guy to fully use the capability of modern F1 car with lever-gearshifts and left foot braking.
So feel free to add and discuss.