He almost killed Rikudo Madara, who was missing a rinnegan, but still had both powers....and he was giving sasuke and naruto trouble.
Then we have this. :lol People say "lol Gai almost killed Juubi Jin" while forgetting that Madara only had the Gudo Dama and Limbo in his fight against Gai, and Minato and Kakashi already made the former useless. So JJ Madara with the techs he used against Gai vs. Gai, Minato, Kakashi, Gaara and Lee. The latter 4 being support. Replace Gai with someone like a hypothetical Edo Madara w/ Hashirama's Senjutsu and Madara would be dead for the simple fact that what Madara used against Gai isn't good enough to destroy PS nor can he take it's attacks with his body. Does that mean Edo Madara w/ Hashirama's Senjutsu is JJ level? Nope.
If it weren't for the Gudo Dama, Obito, another JJ, would've been dominated in his short scuffle with Naruto and Sasuke despite his full power being tiers above theirs.
No Gai limits are SM Hashirama's level. Yes he did do one in on JJ Madara but it's all about match-ups in Naruto.
This basically sums everything up.
That both powers excuse means nothing considering:
-Rinnegan was useless as all he could use with it is Limbo when he only has one eye.
-Rikudo Senjutsu is mainly a multiplier to your power. Standalone the abilities it grants aren't enough.
And no, he wasn't giving Naruto and Sasuke a hard time. He absorbed the Shinju and get a further power up before he fought Naruto and Sasuke and he still failed to pressure them. Ameno and Jiton Rasengan had Madara running to go get his other eye. That is only a fraction of Naruto and Sasuke's full power, which would be Kurama Avatar and PS respectively.
For me it is hard even against Hashirama.
SS is too big and powerful, the 8 gates are insufficient, especially if Hashirama it hides in wood (like Yamato).
Gai dies alone before it can destroy the buddha.
Yes, I know i'm the only one to think so and I don't give a damn.
I honestly can't blame you for believing this, it's not as farfetched as some would believe considering what Shinsuusenju has already survived. Gai still wins though.