(I'm not counting Hugh Watt, because seriously - Who? What?)
Savage - Great guy (to the extent his appeal was kind of cultish), was on the right side of foreign relations during the pre-WW2 era; set up the Ratana accord and basically the entire welfare state
Kirk - #CIAkilledKirk. I can't help but feel, like Fraser, he gets a lot of slack because of the TRAGIC DEATH (I mean, Muldoon's Dawn raids actually started during his premiership, although Muldoon admittedly ramped them up)
Clark - probably about as good as you're going to get from a third way managerialist; although the big controversy about smacking was probably a dumb hill to die on. But a good manager is a good manager, especially as the NEw Zealand political scene was still only just digesting how MMP should work/
Fraser - OK wartime leader, although he never seemed to realise the war ended.
Palmer - did a lot of necessary constitutional stuff (Bill of Rights, removing vestigial British related laws, avoiding further crazy power-grabs like Muldoon tried when he lost), so lean FF; still it's not very ... kitchen table.
Moore - probably could have been a decent PM, but eh.
Rowling - meh
Lange - I mean, he can hardly be mostly blamed for ROGERNOMICS!!! and following Muldoon's wreckage of an economy but still.
Nash - probably would have been better as some sort of diplomat, given that he constantly went on abroad and always spoke in vague Wulfricesque terms ("Labour are not for the waterside workers, and we are not against them"
). Also hadn't mastered the trick later Labour PM's would use of picking up a "big issue" to distract from economic malaise (even though he was basically handed the apartheid rugby thing on a plate).