It's hard to answer without defining what a successful resistance looks like. Going off what you have listed; being involved in the government, and securing protections (which I will mostly consider- protecting land rights), I think it's actually hard to say the Maori made off that well. In fact New Zealand is home to some of the greatest land alienation, and one of the largest foreign settler communities in the Pacific.

Certainly the Maori successfully fought a series of protracted wars against the British empire and forced the empire to deploy more troops to New Zealand than very nearly any other colony. However, the wars were not simply Maori against British; but were much more complicated. Remember that there was no distinct-universal Maori identity until after the British Empire essentially forced it upon the native peoples of New Zealand. You are certainly right in that the Maori at least had some representation in the government as early as the end of the 19th/c thanks to half-Maori men like Te Rangi Hiroa (Sir Peter Buck). But Maori have still been struggling to recoup what was lost and secure fishing access and resource rights till today. A great deal of their land was alienated by the British; and while some has been returned, there are many places in the Pacific that have lost little to no land.

If we wanted to compare them to nearby islands; like New Caledonia; the Maori did mount a more sustained, effective resistance. The French nearly wiped out the Kanaks on New Caledonia and seized a great deal of land during the insurrection of 1878; and used Kanak violence as a pretext to seize or appropriate greater amounts of land. The difference between the Maori and Kanaks comes down largely to guns and tactics. The Maori may have never been united against the British- but they were more united than the Kanaks were until the late 1970s. The Kanaks had less access to firearms and had never engaged in the type of large scale protracted warfare that the British/French and to some extent the Maori had experience with. They had fewer tools with which they could resist the French advance. However; if we zoom from the 19th/c to today; it's harder to say that they are necessarily in a much worse position. Many of the Kanak languages still survive and much of their land has been reclaimed- land in Loyalty Islands was never alienated. And now the Kanak population is roughly equal to the population of the French settler community- unlike the Maori/Pakeha (~white) population.

Peoples on other island nations like Samoa , or the Cook Islands, or Palau have also experienced foreign domination to some extent or another; but they are all independent nations now; nations that still use local languages, and have little to no land alienated to foreigners. So considering their local control, they have done comparatively well. They may have been politically and economically dominated- and perhaps they still are under various neocolonial guises, but on the whole they have protected their land and culture and have a far greater say in their local affairs than the Maori do in New Zealand.

Of course other islands; especially Tonga, would argue that they have never colonized by a foreign power and so they have maintained their identity, land, rights, language, etc; much better than the Maori have.

It sounds to me like your comparison is mostly with Guam, Hawaii, and Fiji; places commonly identified as settler colonies. These are the island groups with the most land alienation and the biggest (re)settled communities. Each of them is of course a very different story; Guam was colonized by the Spanish during the 16th.c; Hawaii was independent far longer than New Zealand, but Hawaiians are perhaps not in quite as an advantageous position today when compared with the Maori. Fiji was the site of a huge cotton and then later sugar industry, which attracted prospective plantation owners from US Civil War refugees (ex-plantation owners who left the US) to small farmers from England that thought they could move up on the world, all of whom participated in the mass importation of laborers from India. Each of these places has a unique history- though Hawaii & Fiji both share a history heavily affected by trade and plantation agriculture, especially in explaining the land alienation & diaspora communities that arrived to work in those industries. In terms of why they maybe ended up less well off than the Maori: the Chamorro on Guam fought a protected war with the Spanish (much like the Maori did, and much like the Maori some allied with the Imperial power using them to help knock off rivals/enemies) and lost the war, they lost because they were never united, and diseases from the Spanish decimated the population during the fighting- unlike with the Maori, whose population suffered far less from disease by the time of their wars with the British (though certainly after contact their population had declined significantly, both from disease and the earlier Musket Wars). The Chamorro were brutally slaughtered and suppressed after the conflict with the Spanish was over and the Spanish took no chances and imported a great deal of Filipino and Mexican conscripts and soldiers to make sure the Chamorro didn't cause any more trouble on what was an important stop in the early Spanish galleon trade. Either the Chamorro were very good at picking and choosing what bits of Spanish culture they liked, or the Spanish were good at acculturating the people they colonized- or maybe both is true- but either way the Spanish radically altered the culture, the language, the organization of the island. The US would arrive and set about doing the same thing; trying to change the language again, change culture, change land divisions; so that today- while there are still Chamorros and people fighting for rights and protection, there certainly is not as much as in New Zealand, largely I would argue because Guam was a colony for hundreds of years longer.

This is so long I will cut myself off here. Hope it helps answer the question some; though I realize I have mostly argued that the Maori are not in fact better off than most Pacific Islanders.

edited for some obvious, painful grammar mistakes

hi! not discouraging other responses, but you may be interested in a few earlier related posts:

• Were the Moaris in New Zealand treated much better than natives in other British colonies? And why?

• How have non-American governments dealt with indigenous peoples who have lived within their territories?

• How are Maori's (treated) different from other native populations?

• Why has New Zealand embraced indigenous culture more than other former British Colonies?

• Why has Australia and New Zealand differed in their treatment of natives?

and this:

• Feature: "Waitangi Day" New Zealand History Mega-Thread