For me, when you have an overtly dominant team, it's far better to have two drivers that are competing against each other pushing each other to the edge, rather than a facto or de facto number one and a number two.
For example when Lewis was racing for McLaren vs his teammate Fernando Alonso, or Lewis vs Jenson Button,
or Lewis vs Rosberg who was also a fantastically quick driver, all world champions, and the championship was all the better for it even though they were in dominant cars for the most part.
Yes, sadly Valtteri didn't quite have it, he had the speed but not the consistency nor the incredible raw talent of Lewis, and neither did Magnussen or Kovalainen.
Lewis has had three immensely talented world-champion teammates, and I would argue one of the very best-ever drivers, Fernando Alonso in his absolute prime.