UPDATE 12/2017 - bonus facts from TLJ
Additionally, from The Last Jedi, we see that Snoke is clearly far superior to Kylo Ren in Force use. For example,
he managed to mind-link (and seemingly physically link, as Kylo Ren has drops of rain from Ahch-to on his hand) Rey and Ren via the Force between galactic distances. That's a power that clearly is missing from Ren's arsenal as he didn't guess that it could have been Snoke doing it and is puzzled as to how they got linked.
Also, in "The Force Hits a Snooze Buttons", we see Snoke effortlessly force-lighting-throw Kylo Ren across the room with contempt and seemingly little effort when he's annoyed with his failure.
Also, Kylo Ren seems to be about equal to Rey (both in theory and in actual practice when they fought mentally and physically on Starkiller Base in TFA); yet
Snoke effortlessly bashes about Rey when she's brought to him.
Kylo could just have been equals with him
Not even remotely likely.
Kylo Ren knows Snoke can crush him, himself. From WGA script:
Snoke is using you for your power.
When he gets what he wants, he'll crush you -- you know it's true.
Kylo hesitates. Somehow, he does know it.
Note that this isn't even Ren saying "I know" - that could be a lie or whatever. It's the narrator saying he knows.
At this point, I think we can close this answer. But let's go for more points for bonus round:
Snoke tells General Hux that Kylo Ren needs further training when he orders him picked up after a fight with Rey on Starkiller Base.
Leave the base at once and come to me with Kylo Ren.
It is time to complete his training.
Snoke implies that he could get into Rey's head. by holographic connection. After Kylo Ren failed. And Ren acknowledges it (from WGA script)
Supreme Leader. I can get the map from the girl. I just need your guidance.
If what you say about this girl is true, bring her to me.
Snoke is the one who trained Kylo Ren. So, he knows everything Kylo Ren does about Dark Side, and - being old enough to have witnessed Galactic Empire rise - presumably a lot more.
Kylo Ren is incredibly powerful with plenty of storm troopers serving under him
This is not a correct assumption either, sorry.
The Stormtroopers serve First Order and Snoke (that is stressed several times in prequel book "Before the Awakening", in the Finn part). Example quote from Phasma (there's more where that came from :)
“A real stormtrooper has no room for sympathy,” Phasma told him. “A real stormtrooper is the extension of the First Order, of Supreme Leader Snoke’s will, nothing less. Do you think the Supreme Leader would have hesitated, FN-2187?”
The stormtroopers report to General Hux (what with him being a General), and Kylo Ren has no military rank that we know of in canon. This is covered in Visual Dicionary, mostly, but also clear from various film dialog, e.g. about soldier performance on Jakku.
This is covered in Visual Dictionary's Kylo Ren's page:
"outside the formal command structure of the First Order."
This seems to - intentionally - directly parallel Episode IV, with Snoke being Emperor, who has two underlings: Tarkin (running the military) and Vader (doing special, Dark-Side-Apprentice-type, assignments). Some troops might report to the Apprentice for the duration of the assignment, but they don't serve "him", they serve the Empire/First Order.