Neither do I, but I heard a lot of them like him, like Boonen, Valverde, Contador, to name a few.
Sagan is a legend of the sport already, and Van Aert obviously want to become one, but there's a long way ahead of him.
Notice that you are mentioning a few established names. And no one is denying that Sagan is an influential and entertaining (well, at least back in the day) rider. But he is not the most sympathetic one. Rarely chats with riders outside of his squad, or they have to be quite a star themselves. And his position battles in sprints and classics, being not shy of some pushing and knocking, also causes frustration in the peloton.Even Yates said he´s a pure class a while ago at Bradley Wiggins show. LINK