I don't think u understood ur own statement, by ur said. Luffy = Ryuma which isn't, unless if u add sum personality now we can agree but even then Oda said that Monsters Ryuma is Mix of Luffy and Zoro. Later on the Story we know Zoro is Direct Descendant of Ryuma so...
Plus Luffy / Joyboy got Compared to Ryuma, because of his feats to defeat Kaido. Not "=" per say