I'm not saying it's the best decision but there are rational explanations.
In an absolute sense, though, it would only be better to rule in Hell than to serve in Heaven if the status of a servant in Heaven was worse than that of a ruler in Hell. Status is relative, but not only relative to the other participants in the study - it's relative to the entire population. I'd prefer to get $10 and have one neighbor get $20 than $8 and $5, because the wealth of millions of people establish the price of goods to me, not one person getting a little more. In a world where a million people get $0, I get $10, and someone else gets $20, I'm relatively wealthier than if a million people still got $0, I got $8, and my neighbor got $5.
Yeah, it might be more economically rational to seek to get $8 million if the entire world was going to get $20 million if I didn't take the option, but then there's the old saying "a rising tide lifts all boats..."
But certainly a font of great insight into base human desire, according to many traditions. It's why "a deal with the Devil" is a trope: the Devil knows exactly what to offer humans in exchange for corruption. So, the GP's quote is apt: an offer to "rule in Hell" vs. "serve in Heaven" is indeed a tempting one for many people.
Do you disagree with Mr Satan's point or do you reject it simply because it comes from him?
So to respond to your question, I do disagree with "Satan's" point.
It is clearly in the interest of an individual to keep all of what they are given, rather than to spend a portion simply to lower the portion given to another.
Along the same train of thought, I would say, "The least of us can achieve greater heights when lifting each other up, than the greatest of us can by pushing each other down."
Very limited principles of equality. Slavery, natives, women, unlanded peasants...
This is true and explains a lot of situations where people seemingly vote against their own self-interest. The fact that responders choose to reject in the Ultimatum Game[1] shows this in action.
But an even more fascinating example than the ultimatum game (sorry can't find the link) is research that shows subjects are willing to pay money to burn the money of others, just so the other test subject ends up with less. For example, offer to give test subject A $10, tell him that you're giving subject B $20, and then give subject A the option of giving up $2 of those $10 just to reduce the subject B's gift from $20 to $5. It was found that a percentage of people will be willing to accept that choice even though it's not the action of someone with rational economic self-interest.
1: https://en.wikipedia.org/wiki/Ultimatum_game