One Piece is pretty entertaining and has being built into a huge franchise, I actually think that one of Naruto's redeeming features its not trying to expand it's universe as much, simply because the storytelling gets hard to handle and Kishimoto is not comfortable with such stakes (imo).
OP is clearly playing on being epic and cashing into the Dragonball feeling that was left empty after the DB series ended. By the fact that it managed to catch the wave and it has a much bigger established fanbase over the years, OP is pretty understandably a great selling manga with all the advantages Naruto has and then some.