First of all, a rich monarch does not equal a good monarch. That is obvious, isn't it?

Arad Doman:

The Merchant Counsil as described in tGS is a bunch of power-hungry arses. A pig made out of paper-mâché would be a better ruler. Alsalam was described as a good king by his friend Ituralde.
Arad Doman is not a large or a powerful nation. We know nothing of how prosperous it was, only that the men have short tempers and the women are hot.

Tear:

Seanchan are better in EVERY way than Tear is. In Tear, every single coin goes to the nobles in the Stone. Even the lesser lords are poor. Everything is restricted, you can't built a city, you need to pay a guide to leave the port and who knows what else.
I suppose this description applies to all Tairen countryside:

--run-down and ramshackle as these rough stone houses, walls slanting as if about to top over. Roofs of cracked and broken slates all looked as if they leaked--. (tDR)

This is how good the Tairen rulers are!
There's the small matter of slavery and damanes, of course, but that's hardly Tuon's fault. And many believe that Tuon will free the damane in the end. And the slaves seem happy?

Amadicia:

Niall was a good ruler, no doubt about that. But Amadicia lacks what the Seanchan have: justice. Whereas Tuon ”radiates order” Amadicians happily hang people if there's a rumor that they're Dfs.
The Seanchan justice system is probably the best and strongest there is. Nobody is above justice and everyone gets it. That's what the people of Altara noticed. As long as you live blamelessly and obey and aren't a channeling woman, you're safe. That's what Tuon upholds, and what many nobles that we've seen can never stomach.


Remember Colavaere and Galldrian from Cairhien? Atrocious people!

Ghealdan is insignificant. They mine and sell alum. Nobody cares about them. And whose fault was it again that Masema brought chaos to the land? The king's!

Tuon has honor and sense of responsibility that many other rulers simply lack. Her concern is for her people, not for herself. She's intelligent, that much is obvious. Willing to adapt her views when needed.

Having said that, I don't particularly like her. But there's no denying that she's among the most capable rulers there is. I would like it if she met Elayne some day. The Aes Sedai monarch who isn't greedy or war-crazed.