Do you think hashirama has more chakra than kurama? he sort of stated something like that this chapter. A few people(kisame, A) have been said to have tailed beast level chakra but this could just be away of saying they have a lot of chakra, besides, kurama has more chakra than the eight tails when it is only half so in full that chkra would have to be godly. saying this madara also has god-like chakra and assuming sasuke will have to reach naruto's level this means he will need chakra levels this high. I say all this to say what we thought were unbelievable chakra reserves from naruto(not including kurama) are actually quite unimpressive when compared to hashirama's, madara's and what I guess will eventually be sasuke's. Naruto's chakra is unimpressive