Zero evidence he's portrayed above. Or Oda is doing a terrible job at portraying that if true.
-> introduced to quote of the pirate king
-> reveal of his son is treated the same ace
-> Akainu holds Roger & Him in the same level when it comes to their bloodline's threat
-> WG sent fleets after Roger when they knew about his whereabouts once he became the PK. They sent a fleet big enough to make blackbeard retreat, once they found Dragon's location.
-> In the very chapter Yonko are introduced, he gets the bigger panel of reveal.
-> Luffy's haki/willpower/ability to attract people (the most powerful ability on the seas), all been compared to Dragon
-> Mans literally freed hundreds of thousands of Celestial Dragon slaves, something only nika's done. His organization is called will of the people.
Oda's done a perfectly fine job in displaying that, y'all just not paying close attention. Him having Sabo as his underling only speaks to his greatness. No different than Luffy having Zoro as his underling speaks to his.
Not to mention more than likely has the highest bounty, with Oda constantly emphasizing Roger & WB having the highest bounty out of pirates and not just in general.