So where is this coming from, looking at opening weekend numbers most will say Godzilla 2014 did $93 million to Kong's $61 million, yes he beat Kong but then compare Kong: Skull Island to King Kong 2005 and Skull Island wins $61 million to $50 million.
So why does that matter, because King Kong 2005 finish with $218 million in the US and $551 million worldwide, Godzilla did $201 million in the US and $529 million worldwide. Despite a stronger start Godzilla finished weaker.
If the same should hold true with Skull Island and the fact it is having a stronger start than the 2005 film it wouldn't be unrealistic. To go with those factors Kong: Skull Island seems to be stronger critically, fans certainly seem to rate it higher (per Rotten Tomatoes), and critics have rated it higher then Godzilla 2014.
And with promotions in China pushing the film, as well as a sort of home field advantage (Legendary Entertainment owners Wanda Group being base there), that may give it a stronger showing there than Godzilla did ($77 million) in what is the second biggest film market. Skull Island also open two weeks after it debut outside of China, Godzilla was nearly a month after.
Only time will tell if this plays out but if it does people may favor Kong to beat Godzilla in 2020, it's going to be some fight.