If any Hulk fan thinks Thanos can beat Hulk, its me but I also believe Hulk would be a threat; its just part of the character...his powers is made to win. I just think Thanos has all the tools to go in areas that would test Hulk strength and durability. Thanos already starts off above Herald strength and durability, he has energy output that also piss on Heralds as well. I don't think anyone here is saying Thanos will piss on himself when he sees Hulk but I also think Thanos acknowledge Hulks power.
Thor said it best, "Hulk, you are by far the strongest being I've ever face".
It's not just a "statement made by Apocalypse", it's Apocalypse conveying the meaning of the readings taken by The Celestial Tech.
It was however talking about the energies that the Hulk generates. Not necessarily the he expends in any given fight.
Part of the purpose of The Celestial Tech that he augmented War with, was to _regulate_ and siphon some of that energy.
Given that it wasn't using all of it, there's no contradiction between Apocalypse's remarks and War's less than impressive performance against Juggernaut.
Apocalypse wasn't talking about the Hulk's personal energy or power there. This was during the period where Hulk and the separated Banner were acting as a link between the 616 universe and the Heroes Reborn universe, and Hulk was leaking massive amounts of unusual energy (i.e. way beyond his norm) as a result. It was a major plot point throughout that period that the Hulk was more powerful than he had ever been as a result, but that he was slowly dying as the energies his body was channeling were killing him.
This was the energy Apoc was referring to so it's not really a comment on Hulk's own power.
There's also the part where Franklin created that entire universe, and he was only a peer to Celestials. Not on the level to overthrow the entire race.
Hell, he even pissed off blasted Ashema to no effect. Even double that energy shouldn't put that on the level Apoc alluded to.
I don't think Apoc's wording should be taken completely literally as in giving him power over all CelestialS. It's possible that the energy that Apoc's tech was reading was Franklin's, as Hulk was essentially acting as a conduit between the 616 universe and Franklin's created one. That would certainly explain why Apoc detected such high readings.
If you want to go roundabouts, to gauge power levels. There's also the business of Onslaught amping himself with Nate and Franklin and still not being strong enough to take out Mindless Hulk.
So, a Celestial's peer and a creature that could create suns, combined together do not possess the physical might to rival Hulk.