I don't think you need too much at retirement, assuming you get the Government super. There is a nifty retirement calculator at the GMI website. If you have a paid for house, you could live a simple but comfortable life with maybe 200K invested in low fee funds in addition to the pension. Have a play around with this:
http://www.gmi.co.nz/investment/retirement-calculator.aspx
For something a little more in-depth, I have countless hours of fun with the FIRE (Financial Independence Retire Early) simulator.
Just on net worth in NZ, the most recent survey was produced last year. The graph referenced earlier in the thread was from 2001 (update below)
http://www.stats.govt.nz chart

[Mod edit: clickable short Stats link]
