As the narrator of the novel, yes Nick is one of the few honest people. Through his narration Nick exposes the corruption and immorality that exists in the upper class residents of East and West Egg, namely Tom and Daisy Buchanan and Jordan Baker. Nick is an outsider in this elite society, so he is more apt to give an accurate depiction of these characters. He tells it like he sees it. While Gatsby is immoral and corrupt, Nick does not hold the same contempt for him as he does for the others. Fitzgerald establishes Nick as a reliable narrator, one whom the readers trust, through statements like this.
Nick is the narrator of the story, so it is hard to tell how honest he really is. The last statement he makes is suspicious, because why would a truly honest person have to support their honesty? I feel that Nick only tells the story to an extent; which makes him look honest.