Hi yosof ... we'll be spending 40 days travelling in NZ shortly and will definitely get Marriott withdrawal symptoms whilst there! I am guessing that the only places big enough for a Marriott would be Auckland and Wellington? There is a good Hilton in Auckland at Princes Wharf but we are using a Novotel in Wellington purely for it's convenience for the railway station ... we have an early departure on the Northern Explorer to Auckland.
The last time that we were in NZ, we found that the larger hotels were fine, the mid range were very variable and the 'mom and pop' guest house sized hotels were great. Most of the time, we used local B&Bs or motels ... the motels are much nicer than those that we have found in the USA or UK. In Christchurch, we used a small hotel called The Grange ... Des and Tracey, who run it, are really lovely people. The bulk of the rest of our stays are in family run B&Bs ... often called 'homestays' as they are usually part of or near where the owners live.
I can give you some recommendations on where we have stayed or will be staying but there isn't much hope of any Elite recognition or Rewards points in NZ.