After the first four, I really wasn't sure who else deserved a mention as I rambled through the possibilities. But, there's at least one more name that I think won't be controversial. After these five, I really can't think of any other general or commander you could really suggest who would have a better claim to the title than these guys. Namely because Sitting Bull's command lasted a significant time period, defeated General Custer and ultimately demanded a level of loyalty from his followers that any general would envy.
Part of the reason that Sitting Bull spent such a long time in the field against the United States is a combination of his stubbornness and the fact that, at the time, it was relatively unwise to trust the government to honor its treaties with the Native Americans. Despite having a relatively small force, and perhaps not completely uniting the Sioux behind him, Sitting Bull was able to effectively engage in small-scale guerrilla tactics.
What set him apart from the other Native American commanders was his refusal to surrender at the Treaty of Fort Laramie (a name I had to look up). I knew he had rejected an opportunity for peace, but we have to look at it from his side. It was not going to be an equal peace; it would have been a kind of peace, but not one that Sitting Bull (or many people today, I imagine) would accept -- have we all been reading our "War Ends and Means?" This idea relates directly to their discussion on kinds of peace.
Now, I don't want to get people picturing that he was in a constant state of battle for the entire time from Laramie to his ultimate surrender (after a brief stint in Canada, eh). But, once Grant gave the green light, that was a possibility that loomed over Sitting Bull for the rest of his run. He must have been charismatic, he drew young men and other chiefs too him. After his fighting days, while he was exploited (though, that might be too harsh a word) in the cowboy shows, he did inspire people. He became something of a romantic figure, which probably has to do with the successful actions at Little Big Horn.
First, Custer's tactics and strategy have a certain panache to them. However, he was also willing to be brutal in his efficiency. Taking hostages of non-combatants is not something we would view highly today, but that is what earned him his victory at Washita, and what he hoped he would be able to recreate at Little Big Horn. Between that and under estimating the size of the force he would come up against, Custer was in for a rude awakening.
Custer's debacle there probably reinforced Sitting Bull and the others' desire to fight more than any thing else. While they had had victories before, this was a major blow. If Sitting Bull and his followers had not been the primary target for the government before hand, after Little Big Horn, he was. Like Yamamoto and Howe, Sitting Bull was unable to turn early victories into a sustained campaign of wins. The U.S. Army was too big, well-equipped and mobile. He withdrew to Canada, ultimately returning to surrender and broker peace.
But, that spectacular victory at Little Big Horn forced the entire government to swing into response. As much as I feel that Custer blundered, Sitting Bull and his forces took advantage of their disorganization to strike decisively. I don't know enough, but even his surrender did not seem so much a surrender as an attempt at reconciliation. Maybe Canada was just too harsh, or maybe he had just gotten tired of fighting, but in the end, Sitting Bull put down his arms to try and forge a more peaceful coexistence. If we remember our Codevilla and Seabury, only ideas can vanquish other ideas, and I think that is ultimately what happened here.
I really can't think of any other enemy commander that is equal in stature to Howe, Lee, Sitting Bull, Yamamoto or Giap. Let me know if you think I've missed any one.