You mention that Cav competed against Kittel and Greipel, but that was only part of his career.
Cav took 20 wins in 4 Tours(08-11), only Greipel was present in one of those, 2011.
Over the next 6 Tours with Greipel/Kittel, Cav had 10 wins. Serious, serious difference there. In fact if you go from 12-17 Kittel has the best record with 14 wins and Cav and Greipel are level on 10. In fact Kittel has a better strike rate at the Tour than Cavendish if you average it out over Tour appearences,
As I keep pointing out, that 08-11 was one of the worst eras of sprinters ever.....well until the current field in this years Tour and that skewers things heavily in favour of Cav.
Kittel and Greipel always had Cav and each other to go against. What other major sprinter was around in 08-11???