Rayleigh & Oden found One Piece too,
Pirate King is Only a Title given to Roger cuz He is a Pirate Captain,
Crocus found the OP too Seagull also
there is only one PK Roger not Ray not Oden
it’s a moot point
Sengoku found One Piece, He wouldn't be called Pirate King, (Rayleigh is called Dark King for example)
Did he find it ?
no
Roger did, Roger influenced the world and made something impossible possible
And no, it's not a Story about Pirate King, the guy wasn't even Main Character in his own Flashback,
It's a Story about "One Piece", a Treasure that is Desired or Feared by both Pirates & Non-Pirates alike,
And finding it can be achieved by a Group, but using it can only be achieved by Luffy, something that Roger failed at,
And who found the OP, who was labeled PK for it. Who paved the way for the new gens ? Who started the golden era of piracy to find the OP ? Spoiler alert : it’s not Sengoku or Oden
Oda even said that He wanted a Story about Vikings, but after He knew that Vikings are a Type of Pirates, He made the Story bigger to include all types of Pirates & Related Communities, and even before One Piece came out, He released Wanted & showed us that He wants to tell many Stories, He said He wanted to draw Samurai, draw Knights, draw Demons, Heroes, Snipers, Deities ... etc
Oda wanted to draw many things and he indeed drew them
But Roger is still Roger
If Oda had kept the same story with Vikings he would have made Roger the Viking King or something like that and Roger would still be the top dog. Just with a different setting. His role would be the same.
Garling is Shanks Father, Garp is Luffy's Grandfather who raised him, Rayleigh is his Mentor who spent more time with him than any SH, Oden literally had like 200 Chapters dedicated to worshipping him, Harald is Viking Roger who as i said are the reason Oda made this Manga ... etc
All important characters indeed
But less important than Roger, less driving for the plot, and with a weaker narrative
Just because One Piece started with Roger & Naruto started with Minato, doesn't mean there aren't others as Strong as them or Superior.
Pirate King is same as Hokage, They are Leaders who inspire their own Communities, but there are like dozen of such Legends,
Roger isn’t Minato, Roger is Hashirama
the one who beat Madara, who created the leaf village, and Naruto wanting to become Hokage
And as Roger there isn’t a single ninja in the old gen or mid gen superior to Hashirama. No one.
Only the old legends and new gens surpassed him like Roger will be surpassed by Joyboy and Imu and Luffy etc.
I’m crying this man certified dgaf anymore 
He testing the editors and higherups with ts