Basically, there are only 3 people stronger than him.
1. Hagoromo (the sage of 6 paths)
2. Kaguya (Hagormo's mother, whom admitted that Kaguya was stronger than him)
3. Madara when he absorbed both the juuib and holy tree.
Current Naruto was even stronger than Madara as the juubi jinshuriki. Basically, he's now so overpowered, that there really can't be any match-ups with current Naruto other than Sasuke, but they're already implied to be equals since they both got half of Hagoromo's power.