Nightmare Moon is the Doctor Doom of My Little Pony.
 
They’re both undoubtedly evil, but they’re also the least likely to screw you over if they win.

@Background Pony #10C7: Which Nightmare Moon had tried to do and failed miserably. Causing her to use her then new-found dream powers to torment Equestria’s citizens. And subsequently cause Nightmare Night to be invented.

@Pepsi_Al  
Giving them dreams that involve the Light not being good.

@Background Pony #83F2: Not likely. Since Nightmare indulges in fear and misery.

What are the odds that Nightmare Moon’s timeline is as tranquil as Celestia’s is because Nightmare Moon used her dream powers to indoctrinate ponies.

@PonyPon: I’ve actually been thinking about that detail. Given what context we DO know, this may be a relatively recent scenario. One that takes place on an alternate timeline following the Summer Sun celebration seen in the first episode.
 
@Nightweaver20xx: There is. And it’s supressed, screaming inside, and wanting to break free from Nightmare’s control.

@Background Pony #7A93  
Plus I’m still willing to believe that there’s still a little bit of Luna kicking around in that black, armored head of hers.

Well, the reason NMM is so much nicer than the other villains is obvious: She wanted to be adored.
 
Sombra enslaved and terrorized the Crystal Ponies before brainwashing them into being his unwilling soldiers. If Nightmare Moon did that, none of their adoration would be genuine because it would all be out of fear or brainwashing.
 
Chrysalis just lorded over everypony like a dictator. The result was that everyone who wasn’t a Changeling hated her, the exact opposite of what Nightmare Moon would have wanted.
 
Tirek was just destroying everything, and thus has no subjects to rule.
 
And Discord was acting out of selfishness, not caring how anyone else felt about him.
 
So of course, Nightmare Moon would be the only pleasant one: If she wasn’t, then she wouldn’t get what she wanted.

@MadVillan  
She’s proactive because she’s greedy and wants the time magic for herself as soon as possible. That’s not a good trait.

I’m ok with this.

@Fwelin  
Only when faced with no other option,however NMM on the other hand is pro-active here. Celestia prefers the defensive option and sending others first when there’s danger.

@MadVillan  
Fixing the townspeople in Lesson Zero, beating Sombra in the past, leading an army against Sombra in person, and fighting Chrysalis is more than just blasting Timberwolves because they’re in the way.

@Fwelin  
Even still, that’s more than we’ve seen Celestia do.

@MadVillan  
She was taking out the Timberwolves because they were in her direct way of getting to the map, not because they were a menace to the citizens of Equestria.

NMM Also seemed to take her role as Equestria’s leader more seriously. I can’t image Celestia ever dirtying her hooves to take out timberwolves like that, or anything else really.

@Philweasel  
And saying she’s a better ruler than Sombra is obvious XP

I’m saying that the world doesn’t completely suck, there’s actually tourism, Nightmare Moon is fairly pleasant to strangers and it’s… kinda pretty.
 
She’s still clearly evil, Rarity and Rainbow Dash are really unpleasant, and the Everfree Forest appears to have expanded it’s borders across Ponyville.
 
Saying she’s a better ruler than Celestia is madness. Saying she’s a better ruler than Discord, Chrysalis or Tirek is certainly a valid opinion.

Maybe… Does this mean we get to wear pajamas all the time?
 
…
 
Because if it does, then I’m totally in on this.

“seem to be loyal of their own will.”
 
There’s your problem: “seem.” Definition: to appear to be true, probable, or evident
 
It also seems OP, that you’re reaching. The evidence on display in this short sequence doesn’t support a good or bad ruler. But based on what we do know from previous examples, NMM is exactly what her name says, a nightmare.

@Fwelin  

 
Exactly. NMM said that Celestia had been banished to the moon for years. We don’t know if that’s 2 or 200. (Granted, Rarity and RD still looked youngish, so let’s shoot for 10.) For all we know, the Everfree Forest might be the nicest place in the whole of Equestria.
 
So please, stop the goofiness of NMM being a better ruler than Celestia.

@Background Human  
“But sir! Every plant and tree will die, owls will deafen us with incessant hooting… the town’s sundial will be useless. I don’t want any part of this project, it’s unconscionably fiendish.”

@Background Human  
The only place we even saw was the castle, and it’s pretty obvious that NMM would want her castle to be nice. Saying that Equestria was doing fine is an enormous stretch.

So here’s my question: do you let Celestia and Luna know about this, or do you keep it to yourself?
 
“I saw what would have happened if Nightmare Moon had been allowed to win. And honestly? Not terrible.”
 
Seems like it’d be weirdly comforting for both of them to know that, even as an evil tyrant, Luna would have taken pretty good care of Equestria in Celestia’s absence.

@Background Pony #6BB1  
‘This family gift of darkness’ works too. :p

I can’t help but read the “Family” watermark as part of the dialog.